
Class T r ^ ?>o 
Book 1^5 

Ci2EmiGHT DEPOSm 



r 






MODERN TUNNELING 



DAVID W. BRUNTON 

ii 
AND 

JOHN A.^ DAVIS 



New Chapters on Railroad Tunneling 

BY 

J. VIPOND DAVIES 



SECOND EDITION 

Revised and Enlarged 



NEW YORK 

JOHN WILEY & SONS, Inc. 

London: CHAPMAN & HALL, Limited 
1922 



3^ 



Copyright, 1914, 
By David W. Brunton and John A. Davis 



Copyright, 1922 

By David W. Brunton, John A. Davis 

and John Vipond Davies 



/ 



-^ 



IP. 



if 



1^ 




PRESS OF 

BRAUNWORTH & CO 

BOOK MANUFACTURERS 

BROOKLYN, N. Y. 



FEB 'iZ 1922 



INTRODUCTION TO SECOND EDITION, 
REVISED AND ENLARGED 

The authors of the First Edition of Modern Tunnehng 
specifically limited the scope of their work by special reference 
to Mine a.nd Water Supply tunnels; that is to say, to those 
tunnels of small size in which the heading was excavated at 
a single operation. 

The increased use of large sized tunnels for railroad and 
highway purposes has advanced rapidly with the development 
of mechanical appliances which aid in the construction of these 
larger sized structures to furnish improved means for con- 
ducting the various classes of transportation. Consequently 
the authors of the original volume felt it to be desirable to 
widen the scope of the work by the addition of new matter 
deahng with the various classes of large sized tunnels, and the 
present writer was invited to undertake the work of the enlarge- 
ment of the subject matter. As a result of his great regard 
for Mr. D. W. Brunton, and the substance contained in the First 
Edition, the present author agreed to write this further work 
and presents it herewith as a brief study of enlarged tunnel 
construction. 

It is fully appreciated that book space of ten times the extent 
of the present volume would hardly cover the full scope, but it 
is hoped that the suggestions herein given will be helpful to 
the student of the subject. It will be realized that all matter 
in the original volume is equally suitable and applicable to the 
building of the larger sized tunnels up to the point of enlarge- 
ment of the headings to the full sized section. 

The author is indebted to so many Engineers, Corporations, 
Authors and PubHshers, for matter which has been woven 
into this revised edition, that it would be impracticable to select 
individuals to whom to express the sense of that debt; but begs 
herewith to offer to all those who are referred to or indicated 
in the text, his acknowledgments and appreciation. 

iii 



1 



CONTENTS 

PAGE 

Chapter I. 

Introduction 1—4 

Purpose of book i 

Scope of book • 2 

Acknowledgments 3 

Chapter I!. 

The history of tunnehng 5~34 

Tunnels driven by hand 'drilHng 12 

Mining and water tunnels driven by machine drilling . . 19 

Railway tunnels 24 

Chapter III. 

Modern mining and water tunnels 35~52 

Resume of data 35 

Modern tunnels described in engineering magazines ... 49 
Chapter IV. 

Choice of power for tunnel work 53~79 

Sources of power 53 

Production of power 54 

Water powder 54 

Steami 58 

Internal-combustion 58 

Electric motors 64 

Transmission of power .64 

Choice of power 65 

Duration of plant 65 

Accessibility 66 

Cost of installation 66 

Labor 74 

Fuel consumption 74 

Thermal efficiency 75 

Purchase of current 76 

Interest and depreciation 77 

Conclusions 78 

Chapter V. 

Air compressors •. . 80—110 

Power required 81 

Capacity 82 

Types 85 

Straight line 85 

Duplex 88 

Turbo-compressors 91 

Comparisons 94 

V 



VI CONTENTS 

Chapter V. 

Air compressors — {Continued) page 

Regulation 97 

Steam driven 97 

Water driven 98 

Electrically driven 99 

Heat loi 

Heat produced . loi 

Dangers of. high temperatures loi 

Removal of heat 102 

Intercooling 104 

Moisture 104 

Accessories 106 

Precoolers 106 

Aftercooling 106 

Air receivers 107 

Drains 108 

Conclusions 109 

Chapter VI. 

Ventilation Ill— 124 

Machinery ill 

Direction of current. . 113 

Capacity 115 

Pressure 118 

Size of pipe 121 

Comparison of fans and blowers 122 

Conclusion 123 

Chapter VH. 

Incidental surface equipment . . . - 125—129 

Drill sharpening machines 125 

Air meters 127 

Chapter VIII. 

Rock-drilling machines 130—162 

Types 130 

Pneumatic drills 130 

H^'draulic drills 138 

Electric drills 141 

Gasoline drills 147 

Merits of each type 147 

Pneumatic drills 147 

Hydraulic drills 157 

Electric drills 157 

Choice of drills 160 

Chapter IX. 

Haulage 163-180 

Tunnel cars 163 

Loading machines 1 70 

Motive power 173 

Dumping devices 178 



CONTENTS vii 

Chapter X. page 

Incidental underground equipment 181—209 

Tunneling machines 181 

List of tunneling machine patents 188 

Illumination 201 

Telephones 205 

Incidentals 207 

Chapter XI. 

Drilling methods 208-235 

Number of shifts 209 

Mounting 212 

Number of holes 218 

Direction of holes 221 

Depth of holes . 229 

Chapter XII. 

Blasting 236-259 

Ammunition 236 

Loading 248 

Firing 254 

Storing 257 

Thawing 258 

Chapter XIII. 

Methods of mucking 260—269 

Number of men . . 260 

Positions of working 261 

Handling cars 263 

Use of steel plates -. 267 

Chapter XIV. 

Timbering 270—288 

Materials 270 

Types 273 

Chapter XV. 

Safety 289—327 

Causes of accidents 290 

Falls of roofs 290 

Use of explosives 292 

Premature explosions 296 

Misfires 299 

Suffocation by gases from explosives . 303 

Suffocation by gases from other sources 305 

Haulage 309 

Electricity 311 

Fire 313 

Water 315 

Intoxication 318 

Prevention of accidents 318 

Precautions for the manager or superintendent . . .319 

Precautions for the foreman . . . 321 

Precautions for the miner 324 



i 



Vlll CONTENTS 

Chapter XVI. page 

Cost of tunnel work 328—359 

Coronado tunnel 329 

Gunnison tunnel 331 

Laramie-Poudre tunnel 332 

Los Angeles Aqueduct 333 

Lucania tunnel 343 

Marshall- Russell tunnel 344 

Mission tunnel 345 

Newhouse tunnel 346 

Rawley tunnel 347 

Roosevelt tunnel 348 

Stihvell tunnel 352 

Strawberry tunnel 353 

Chapter XVI J. 

Bibliography 360-419 

Tunnel descriptions 360 

Water power 369 

Steam power 371 

Internal-combustion power 373 

Electric power 378 

Compressed-air power , . . . . 380 

Power transmission 381 

Choice of power 382 

Power plant descriptions 382 

Air compressors 385 

Compression of air 388 

Compressed-air accessories 1 .... 391 

Ventilation 393 

Air drills 394 

Hydraulic drills 395 

Electric drills 396 

Drilling accessories 397 

Haulage 398 

Tunneling machines 401 

Illumination 402 

Methods of tunnel driving 402 

Drilling methods 405 

Blasting methods 406 

Blasting supplies 408 

Mucking 41 1 

Timbering 411 

Speed records 4^2 

Safety and health 4^4 

Costs 418 



I 



CONTENTS IX 

Chapter XVIII. page 

Railroad Tunnels 420-460 

Introduction 420-424 

Economics 424-426 

Design 426-458 

Geology 426-429 

Cross-section 429-431 

Alinement . . . . . 432 

Lining . 432-447 

Backing of lining 447-448 

Waterproofing lining 448-451 

Drainage and pumping 451-456 

Ventilation . . 456-457 

Lighting 457-458 

Contract Bids 458-460 

Chapter XIX. 

Construction 461-481 

Foreign systems. . 461-462 

Survey 462-465 

Plant Installation and Equipment applicable to all classes of 

enlarged tunnels 465-481 

Plant 465-467 

Air Compressors 467-468 

DriHs 468 

Loading equipment 468-470 

Haulage equipment 470-475 

Drainage and pumping 475-476 

Ventilation 476-477 

Lighting 477-47^ 

Surface equipment 478-479 

Camp. 479-481 

Chapter XX. 

Hard Rock Tunnels (Self-supporting) 482-509 

Excavation methods 482-484 

Size of heading 484-486 

Comparative cost of tunnel excavation in trap rock, 

years 1906 and 1907 486-490 

Drill mounting 490-497 

Top or bottom heading 497-499 

Center heading 499~505 

Overbreakage and packing 505-508 

Rotary cutters 508-509 

Advanced test drilling 509 

Chapter XXI. 

Loose Rock and Soft Ground Tunnels 510-543 

Excavation methods 510-517 

Needle beams 517-518 

Steel sets 518-520 



X CONTENTS 

Chapter XXI. — {Continued). 

Loose Rock and Soft Ground Tunnels — {Continued) page 

Pilot tube method 520 

Lining methods 520-525 

Collapsible forms 525-527 

Pneumatic placement of concrete 527-531 

Precast block lining 531 

Brick lining 531-532 

Cement Gun 532-533 

Liberty Tunnels 533^542 

Cost of soft ground tunnel 542-543 

Chapter XXIL 

Subaqueous Tunnels 544-567 

Tunneling shields 545-550 

Shield equipment 550-553 

Wood lining 553 

Roof shields 553-554 

Caisson method 554-557 

Cofferdam methods 557-558 

Construction Plant 558-563 

Boilers 558 

Compressed Air 559-561 

Air Locks 562 

Electricity 562-563 

Hydraulic power 563 

Miscellaneous plant 564 

Cost of Subaqueous Tunnels 564-567 

Shield driven, iron lined 564-566 

Trench type 566-567 

Bibliography to Chapters, XVIII-XXII ....... 568-576 

Appendix (outline of tunnel data) 577-582 



I 



CHAPTER I 

INTRODUCTION 
PURPOSE OF BOOK 

Up-to-date information concerning tunneling methods is 
difficult to obtain. There are but few books on the subject, 
and much of the material they contain, although it is very 
interesting and valuable historically, is now obsolete. The 
engineering periodicals, it is true, endeavor to keep abreast of 
the times and there are several of which scarcely an issue ap- 
pears without some article bearing upon tunnel work. But the 
very multiplicity of these magazines prevents one from reading all 
of them regularly, and the foreman or superintendent in charge 
of a tunnel, or the mining engineer designing one, and especially 
the business man financing the project, has no time for a labo- 
rious search after scattered articles in order to determine the 
present status of tunnel work. Then, too, knowledge of new 
methods travels slowly. Inventions and improvements of 
definite and practical value in mining as well as all the other 
industries, and important discoveries in science, frequently 
remain in the note-book of the investigator, or, as theses, are 
buried in university libraries or may be published only in the 
very locally distributed journals of small scientific societies. 
In biology, the work of Mendel on heredity (whose experiments 
in his cloister-garden are the foundation of a new conception 
of the nature of living things on the part of biologists, which 
bids fair to exert an influence not less than that associated with 
the name of Darwin), although pubKshed locally by him in 1865, 
remained unknown to the scientific world until its simultaneous 
discovery by three independent workers in 1900. In astronomy, 
the invention of the achromatic lens, without which the modern 
telescope would not be possible, by John Dolland in 1758, was 
antedated some twenty-five years by the investigations of Chester 
Moore Hall. So also in tunneling, up-to-date methods and equip- 

1 



2 - MODERN TUNNELING 

ment that ai'e proving safe, efi&cient, and economical may be 
totally unknown outside the district in which they originate. 
This book is intended to supply, if possible, such data concerning 
timnehng methods in the United States, and to make suggestions 
that, it is hoped, may result in a saving to the mining industry 
of life, energy, and capital that would otherwise be expended for 
inefficient or useless work. 

In most of the published accounts of tunnel work, the writers 
usually do not attempt to criticise the methods they are de- 
scribing. It is customary for such articles to contain accurate 
descriptions of equipment, various phases of working operations, 
and occasionally figures showing the cost of the work, but rarely 
do they include a discussion of the means for preserving the 
health and life of the employees, or data bearing upon the choice 
and efficiency of equipment or an analysis of methods and costs. 
As a result, the reader in drawing conclusions is dependent 
wholly upon his own resources. In this volume, on the con- 
trary, the making of such analyses will be a primary considera- 
tion. It is desirable, nevertheless, in an impartial, disinterested 
book of this character to use constructive rather than destruc- 
tive criticism. For that reason emphasis will be placed upon 
safe, efficient, and economical methods, and upon good points 
of equipment, while bad practice and obsolete machinery will 
be ignored except, perhaps, as examples of the inadvisable or as 
they have some bearing historically. Thus the authors hope to 
set forth a guide for future work rather than an unillumined 
record of past or present achievement. 

SCOPE OF BOOK 

This book will be confined chiefly to tunnels and adits* 
for mining purposes, such as drainage, transportation, or de- 
velopment, but it will also include those which are used to carry 
water for power, irrigation, or domestic use, in which the essential 

*It has been suggested by prominent authorities that the word " tunnel " 
be restricted to the • designation of such nearly horizontal passageways as 
extend completely through a mountain or hill from daylight to daylight, and 



INTRODUCTION 3 

features are practically identical with mine tunnels. Tunnels 
of this sort are generally driven through at least fairly hard rocks 
in contrast to ordinary soil, quicksand, and other heavy material 
of a treacherous nature, and they are practically never driven 
through modern river-bed deposits. It will not be necessary, 
therefore, to consider the special methods and equipment for 
tunnel work in such materials. A distinction will be made be- 
tween tunnels or adits for which the excavation is wholly or in 
a large part in material containing no ore and those which follow 
the vein through any irregularity in direction. As far as possible, 
the discussion will be limited to the former, because in the latter 
instance the methods employed in driving along a vein are 
usually more akin to the distinctive operations for removing ore, 
and are, therefore, not so apt to be good examples of tunnel 
practice. 

ACKNOWLEDGMENTS 

In the preparation of this book valuable assistance has 
been received from numerous sources. The writers are deeply 
indebted to the officials of the New York Board of Water Supply, 
of the Los Angeles Aqueduct, of the United States Reclamation 
Service, and the Bureau of Mines, and to the officers, managers, 
superintendents, and foremen at the different tunnels, for favors 
granted, for information suppHed, often at no little inconvenience,' 
and, above all for that hearty co-operation which has been an 
unfaiHng source of inspiration. Many thanks, also, are due the 

the words "adit" and "drift" be used only for similar galleries which enter 
from the surface and serve to drain a mine or furnish an exit from the work- 
ings, but do not continue entirely through the hill. Such definition is eminent- 
ly desirable from a strict technical viewpoint and would undoubtedly result 
in a much to be desired precision of diction, but, although it was proposed 
over thirty years ago and the suggestion has been repeated several times 
since, it has been found difficult, if indeed possible, to establish it practically. 
The American usage of referring to any horizontal gallery as a tunnel, without 
considering its extent completely through a hill or not, is so firmly fixed in 
our mining literature (being used by authors and editors alike), and among 
practical mining men generally in this country, and is even embodied in the 
United States mining laws, that the proposed restriction has been thought 
scarcely justifiable in a practical work of this character. 



^: 



4 MODERN TUNNELING 

manufacturers of equipment and materials used in tunnel work 
for their promptness and courtesy in furnishing catalogues, 
data of tests, and similar material, and in supplying photo- 
graphs, blue-prints, and cuts, which have been of great assis- 
tance in the preparation of many of the illustrations in this 
volume. Obligation is also acknowledged for many valuable 
suggestions obtained from articles in engineering periodicals 
and from books on tunneling and related subjects. 



CHAPTER II 
THE HISTORY OF TUNNELING 

The art of excavating underground passageways has been 
known to mankind for many centuries. The ancient Egyptians 
and Hindus employed it in the creation of many wonderful 
subterranean temples and sepulchers in hard rock, and similar 
monuments are found in the works of the Hebrews, Greeks, 
Etruscans, Romans, Aztecs, and Peruvians — in fact, of all 
ancient civilized peoples. 

It is not surprising that the Egyptians, with their wonderful 
knowledge of quarrying as well as many other useful arts, 
should have been versed in methods of underground rock ex- 
cavation. Remains of their work, some of which dates back 
to 1500 B.C., may be found in the grottos of Samoun, the tombs 
near Thebes and Memphis, the catacombs of Alexandria, and 
the temples of Ipsamboul. A gigantic tomb has been found at 
Abydos, which was cut in the soKd rock during the Twelfth 
Dynasty by Senwosri HI.; also Rameses IL, who is perhaps the 
best-remembered personage of these ancient times, constructed, 
either because of vanity or the great length of his reign, many 
rock-cut temples, the grandest of which is probably that of Abu 
Simbel. 

The work was performed with hand tools, and the labor neces- 
sary to have fashioned monuments of such magnitude and 
grandeur niust have been stupendous. For cutting granite 
and other hard rock, the workmen used saws of copper which 
were either fed with emery powder or were set with teeth of that 
abrasive. A similar method was employed as early as the Fourth 
Dynasty for circular holes which were drilled by a tube having 
fixed teeth, or which was fed with emery powder. For removing 
rock in a quarry or in a tunnel, grooves varying in width from 
4 to 20 inches were made on four sides of a block, which was then 

5 



b MODERN TUNNELING 

broken out by the swelling action produced by soaking with 
water a number of wooden wedges driven into these grooves. 

The excavations in India probably number at least a thousand, 
the majority of which are of Buddhist origin. They are usually 
of two types — chapels and monasteries. The former consist of 
a nave with a vaulted roof, separated from the side aisles by 
columns, and containing a small chapel at the inner circular end. 
The latter consist of a hall surrounded by a number of cells for 
the residence of monks and ascetics. 

Most of the Indian excavations are of much later date than 
those in Egypt. The earliest, the Sudama, or Nigope, cave, was 
constructed probably about 260 B.C.; the Lomas Rishi was built 
about 200 B.C., and those of Nassick about 129 B.C. These 
earlier caves imitated very closely contemporaneous timber- 
roofed temples, and for this reason the columns all slope inward, 
copying with great fidelity of detail the rafter supports of the 
wooden temples. In the Karli caves (about 78 B.C.) this feature 
is absent; the columns of the nave are quite plumb and the per- 
fection of architecture and ornamentation is unsurpassed by any 
of the later Hindu rock-temples. The galleries and rooms of 
the caves of Ellora contain a total of nearly five miles of sub- 
terranean work. Although the builders may possibly have 
known of gunpowder, it was not used in the construction of these 
tunnels, which, like all the preceding works, were accomplished 
laboriously with hand tools and probably by slave labor. The 
caves of Salsette belong to the sixth century a.d., while those at 
Elephanta were constructed about 800 and the Gwalior temples 
were excavated still l-ater during the fifteenth century. 

Modern archaeological investigation indicates that tunneling 
was possibly known to the Minyae, an ancient Grecian people 
dating back beyond 2000 B.C., whose cycle of myths includes, 
among others, that of the Argonautic Expedition. A series of 
shafts, sixteen in all, are to be seen near Lake Kopais in Boeotia, 
which are supposed to have been constructed by these peoples 
for the ventilation of an ancient drainage tunnel. The shafts 
are 200 to 1,000 feet apart, 6 to 9 feet wide, and have a maxi- 
mum depth of 100 feet. The tunnel was probably the enlarge- 



THE HISTORY OF TUNNELING 7 

ment of a natural watercourse such as are commonly found in 
similar calcareous rocks. Krates of Chalcis, a mining engineer 
who Hved in the time of Alexander the Great, is credited his- 
torically with an attempt to drain this lake by utilizing and 
enlarging natural watercourses. 

Although the exact date of the introduction of mining into 
Attica, probably from the Orient, is unknown, it seems to have 
been subsequent to the time of Solon (about 600 B.C.). By 489, 
it is certain that the silver mines of Laurium were yielding a 
highly satisfactory return, and at the instigation of Themas- 
tocles, the net profits from them were applied by the Athenians 
to the construction of a fleet, so that these mines no doubt con- 
tributed largely to the prosperity and power of Athens. The 
workings, approximately two thousand in all, consisted of shafts 
and galleries in which the rocks were hewn out wdth hand tools 
and brought to the surface on the backs of slaves. Air was 
supplied to the large underground stopes or chambers by venti- 
lating shafts about 6 feet square and from 65 to 400 feet deep. 

Gold was mined in Macedonia and Thrace at least as early as 
the fifth century B.C., and Herodotus mentions a tunnel in the 
island of Samos built in the sixth century, which was 8 by 8 feet 
in cross-section, and nearly a mile long. 

The x^ztecs w^ere well acquainted with mining, and they 
secured copper from the mountains of ZactoUan, while the mines 
of Tasco furnished silver, lead, and tin; and the extensive gal- 
leries and other traces of their labor were of great assistance to 
the early Spanish miners. With no knowledge of iron, although 
iron ore was very abundant, their best tools were made of an 
excellent substitute in the form of an alloy of copper and tin. 
With tools of this bronze, they could not only carve the hardest 
metals, but with the aid of powdered silica they could cut the 
hardest minerals, such as quartz, amethyst, and even emerald. 

Although the mines of the ancient Peruvians were Httle more 
than caverns excavated in the steep sides of mountains, never- 
theless they knew of the art of tunneling, as is shown by tunnels 
of their aqueducts and by the extensive tunnel which they built 
to drain Lake Coxamarco. They, too, had no knowledge of 



8 MODERN TUNNELING 

iron, and their tools were made of an alloy of copper and tin, 
which they probably discovered quite independently of the 
Aztecs, whom they rivaled also in the cutting of gems. 

The Romans, however, were undoubtedly the greatest tunnel- 
builders of early history. They drove tunnels for passage, 
drainage, water supply, and mining, not only in Italy, but wher- 
ever their conquests led them, as is evidenced both by records 
and by old workings left behind in the countries they dominated. 
One hardly needs to mention the numerous aqueduct tunnels and 
sewers of the ancient city of Rome, some of which are in use 
to-day, attesting the abihty of the Romans in this branch of 
engineering. Remains of their work, many of them remarkably 
well preserved, have been found in France, Switzerland, Portu- 
gal, Spain, Algiers, and even Constantinople. 

Their tunnels were of no mean size. A road tunnel near 
Naples constructed, according to Strabo, about 36 B.C., was 
approximately 4,000 feet long, 30 feet high, and 25 feet wide. 
About 359 B.C., Lake Albanus, which lies about fifteen miles 
southeast from Rome, was tapped for its supply of clear water 
by a tunnel over a mile long, 8 feet high, and 5 feet wide. 
Possibly the greatest Roman tunnel was driven by the Emperor 
Claudius to drain the overflow waters from Lake Fucinus, 
which is situated about seventy-five miles nearly due east of 
Rome and has no natural means of outlet. This tunnel, com- 
pleted in 52 A.D., after eleven years' labor, is over three miles 
long, and was designed to be 19 feet high and 9 feet wide; but 
it appeared to have been even larger than this when, in 1862, 
it was reopened to secure valuable land beneath the lake. 

These works seem all the more marvelous when one considers 
the primitive methods available at that time. Explosives were 
unknown, and machinery was not then used in mining. Rock 
openings were usually made by chipping, by channeling and 
wedging, as in Egypt, or by cutting large grooves around the 
block to be excavated, using hand tools made of iron, copper, 
and bronze, although it is quite possible that for certain classes 
of stone-cutting, diamonds or some similarly hard minerals were 
employed in conjunction with primitive tube-drills and saws. 



THE HISTORY OF TUNNELING 



9 



These methods were often supplemented by fire-setting, a method 
chiefly employed, however, in the large chambers or stopes, 
and not well adapted for driving small tunnels. It consists 
simply of heating the rock to a very high temperature and 
quenching suddenly with water (or sometimes with vinegar in 
calcareous rocks), producing shattering and disintegration be- 
cause of sudden con- 
traction. Many writ- 
ers have described the 
intense and fearful 
sufferings of men en- 
gaged in this work, 
usually slaves and 
prisoners of war who 
perished by the thou- 
sands — a fact, how- 
ever, of little concern 
to the ancient builders. 
The value of Spain 
as a storehouse of 
precious metals, oft'- 
setting somewhat the 
influence of Eastern 
wealth, was well ap- 
preciated by Roman 
leaders, and an armed 
force for the pro- 
tection of the mines 
was maintained there 
constantly, in many 

cases at the cost of serious political and financial embarrass- 
ment at home. In southern Spain, where the numerous silver 
and copper mines contained much water, Roman tunnels are 
very common. They are remarkable for their small size, being 
usually about 5 feet in height and, where timbered, from 
16% to 36 inches in width, a fairly typical one being shown in 
Figure i. This adit, as far as explored, has a length of 1,850 




Fig. I, 



Section of an old Roman adit 
in hard slate. 



10 



MODERN TUNNELING 



1 



_S1 



-l-^H^ 



3M X CM 



feet and a maximum depth of 183 feet. The timbered openings 
are even smaller than this, a fair type of them being shown in 
Figure 2, which gives the dimensions of the openings and the 
timbers supporting it. The particular tunnel from which this 
section was taken is 2,300 feet long and 
has a maximum depth of 215 feet. 

As nearly as can be ascertained to- 
day from discoveries in them of various 
objects of interest, including coins, it is 
certain that these adits must have been 
driven very early in the Christian era. 
Toward the latter end of the period in 
which these particular tunnels were used 
by the Romans, attempts were made to 
work the ore bodies below them by rais- 
ing water from the lower stopes by 
means of slave-operated water-wheels. 

Since artificial ventilation by means 
of blowers was at that time unknown, 
like most of the Roman tunnels, these 
were ventilated by shafts which were 
spaced in the tunnel illustrated above 
at about 25-meter intervals; in order, 
also, to minimize the depth to which the 
shafts were sunk, the tunnels corre- 
sponded very nearly in their course to that of the valleys or 
gulches above them, instead of being straight, as is the usual 
modern practice. Like the adits, the ventilating shafts were 
remarkably small. Where timbered, they were usually about 
2 feet 10 inches square in the clear, and where the rock would 
stand without timbering they were circular and generally did 
not vary much from 2 feet 4 inches in diameter. 

With the fall of the Western Empire, tunnel work in Europe 
practically ceased for many centuries. Some excavations were 
made, it is true, for tombs and the crypts of monasteries; and 
underground passages leading to a secluded exit, to furnish the 
occupants a means of escape in time of defeat, were a necessary 



Fig. 2. Section of timbered 
Roman adit. 



THE HISTORY OF TUNNELING 11 

part of the equipment of each castle. Crude attempts at mining, 
also, were practiced in Germany. The Teutonic tribes, whose 
main occupation was warfare and who were savage, barbarous, 
and essentially nomadic at the time of the conquests of Juhus 
Caesar, had probably learned from the Romans the value of gold; 
later, somewhat tempered and softened possibly by the civihza- 
tion they had destroyed, they began to search for precious 
metals and to pursue other peaceful occupations. 

During the Middle Ages tunneling was devoted almost exclu- 
sively to the needs of war and was seldom employed for con- 
structing aqueducts or other public works. There is, however, 
a record of a road tunnel begun in 1450 by Anne of Lusignan. 
It was intended to pierce the Alps at an elevation of nearly 
six thousand feet, and afford better means of communication 
between Nice and Genoa, but was never completed. Work 
was subsequently resumed in 1782 by Victor Amadeus III., 
but was finally abandoned twelve years later, after a total of 
nearly eight thousand feet of tunnel had been constructed. 

Although gunpowder in Europe, according to the consensus 
of opinion, was probably invented early in the fourteenth 
century and by the end of the sixteenth century was very com- 
monly used in military operations for gunnery and for blowing 
up fortifications, it was not applied directly to mining or tunnel 
operations during this period. Agricola's ''Bergwxrck Buch" "^ 
(pubHshed by Basel in 162 1), the third edition of ''De Re 
MetalHca," pictures the Roman methods and of hand work and 
fire-setting as the usual means of mining at that time. 

In the year 16 13, Martin Weigel is said to have introduced 
gunpowder into mining work. Gatschmann describes the use 
of wooden plugs for tampiQg at this time, which were later 
(about 1685) supplanted by clay. August Bayer (''Das Geseg- 
nete Markgrafenthum Meissen," 1732) and Henning Calvor 
(" Nachrichten liber das Berg- und Maschinenwesen am Harze," 
etc.) also confirm the date of 16 13 for the invention of drilling 
and blasting, but Honemann and Rossler make it fifteen or 

* A complete English translation is now published. Hoover, H. C, and 
Hoover, L. H., De Re Metallica, 637 pp., London, 1912. 



12 MODERN TUNNELING 

twenty years later. Whatever may have been the date when 
blasting was first used in mining, it is certain that the practice 
had become fairly common by 1650, for powder is mentioned 
as having been purchased for the Harz mines as early as 1634, 
drill-holes are reported at Diillen, which bear the date of 1637, 
and blasting is known to have been introduced into the Freiberg 
district in 1643. 

The use of gunpowder in mining gave a new impetus to that 
industry which produced a large corps of men trained to over- 
come the difhculties of underground drifting, and it is not sur- 
prising therefore to note soon after an increased activity in 
tunnel work for other purposes. The chief of these allied 
interests was transportation, and in the eighteenth and early 
part of the nineteenth centuries a large number of tunnels were 
driven in connection with the canals, which, aside from wagon 
roads, were the onl}^ highways at that time. Later the develop- 
ment of steam railroads and the desirability of maintaining 
level gradients created a still greater demand for tunnel con- 
struction. A brief review will be given of the more important 
tunnels constructed for these purposes, both abroad and at 
home. 

TUNNELS DRIVEN BY HAND-DRILLING 

The first modern tunnel to be constructed for commercial 
transportation was the Malpas tunnel on the Languedoc Canal 
in France. It was 515 feet long, 22 feet wide, and 27 feet high, 
and was built between 1679 and 1681 * by Riquet, a French 
engineer. Although this tunnel showed that canals could be 
constructed through country before thought impassable, further 
advantage was not taken of this fact in France until nearly a 
hundred years later, when the Rive de Gier tunnel (1^656 feet 
long) was constructed on the Givors Canal in 1770, and the 
Torcy tunnel (3,970 feet long) on the Center Canal was built 

* The writers wish to acknowledge their especial indebtedness to Henry 
S. Drinker, from whose monumental work on tunneling this and other valuable 
information concerning the earlier history of tunnel driving has been ob- 
tained. 



THE HISTORY OF TUNNELING 13 

in 1787. The Tronquoy and the Riqueval tunnels on the 
St. Quentin Canal were started in 1803 and the Noirou tunnel 
(approximately 39,400 feet in length), on the same canal, was 
begun in 1822. On the Bourgoyne Canal, the St. Aignan 
tunnel was started in 1824, so that by the middle of the nine- 
teenth century nearly twenty canal tunnels in France had 
been constructed, having an aggregate length of nearly 93,500 
feet. 

The earliest transportation tunnel in England was the Hare- 
castle, situated on the Grand Trunk Canal, which was begun in 
1766 and opened for trafhc in 1777. This tunnel was 8,640 feet 
in length, 9 feet wide, and 12 feet high. There were originally 
four other tunnels, but of shorter lengths, also on this canal. 
The Harecastle tunnel was found to be too small to accom- 
modate the trafhc through it, and was replaced in 1824 by a 
parallel tunnel, which was 16 feet high and 14 feet wide, 4 feet 
9 inches of this width being used for a tow-path. The Sapperton 
tunnel on the Thames-Medway Canal was started in 1783. It 
was approximately 12,500 feet long, and six years were employed 
in its construction. The next large canal tunnel in England 
was the Blisworth (9,250 feet long), on the Grand Junction Canal, 
which was started in 1798, and required seven years for its 
completion. In 1856 there were over forty-five tunnels on the 
various English canals, aggregating some 220,000 feet in length. 

The first canal tunnel in the United States was the Auburn 
tunnel at the Orwisburg Landing on the Schuylkill Ns^vigation 
Canal. The tunnel (which was 450 feet long, 20 feet wide, and 
18 feet high) was begun in 1818 and opened for traffic in 182 1. 
The hill it pierced was composed of red shale, and the highest 
point was only forty feet above the top of the tunnel. The 
tunnel was shortened in 1834-37 and again in 1845-6, and was 
finally taken out altogether in 1855-6 by an open cut. The 
''Summit Level,'' or Lebanon Tunnel on the Union Canal, begun 
in 1824 and finished in 1826, was the second canal tunnel in this 
country. It was originally 720 feet long, 18 feet wide, and 15 
feet high, being driven through argillaceous slate at a total 
cost of $30,464. It was followed by the "Conemaugh" and 



14 MODERN TUNNELING 

"Grant's Hill" tunnels on the Western Division of the Pennsyl- 
vania Canal (1827-30), the Paw-paw tunnel on the Chesapeake 
and Ohio Canal (1836), and two tunnels on the Sandy and 
Beaver Canal, Ohio (1836-38). 

The first railroad tunnel of which we have any record was 
the Terre Noire tunnel, near St. Etienne, France, on the Roanne- 
Andrezieux horse railroad. This tunnel, which was begun in 
1826, was 4,920 feet long, 9.8 feet wide, and 16.4 feet high. 
Some fourteen other tunnels were built on the road from St. 
Etienne to Lyons between 1826 and 1833. The first tunnels 
on a railroad using steam locomotives were those on the Liver- 
pool and Manchester Railway, constructed between 1826 and 
1830. It was on this road that the famous trial between the 
"Rocket," "Novelty," and "Sans Pareil" locomotives took 
place in 1829. The following summary of early railroad tunnel- 
building in Europe is quoted from Drinker's "Tunneling," 
page 19. 

'' Tunnels, of course, multiplied rapidly in England with the 
extension of railways, and during the twelve or fifteen years 
following the construction of the Liverpool and Manchester 
line, there were a large number of tunnels built throughout 
the kingdom, among them being the famous Kilsby, Box, and 
Woodhead tunnels. The first tunnels on a steam railway in 
France were those built on the St. Germain line in 1837. Sub- 
quently, the ones on the Versailles, the Gard, and the Rouen 
lines raised the total length of tunnels in France in 1845 to 
12,833 "^' (42,105 feet). The report of the Corps des Ponts 
et Chaussees on tunnels for 1856 shows at that date a total on 
French railroads of 126 tunnels, of a total length of 65,106 
meters. Among the noted early French tunnels may be cited 
the Nerthe, Arschwiller, Rilly, La Motte, Lormont, and Alou- 
ette. In Belgium, the Cumptieh tunnel, built in 1835, on the 
Xhemin de I'Etat,' seems to have been the earliest. In 
Germany (Prussia and other States) the earHer lines were so 
located as not to require much tunnel-work; and Oberau tunnel 
(1839), on the Leipsic-Dresden line, in Saxony,- was the first. 
In Austria, Rziha gives the Gumpoldskirch tunnel as the 



THE HISTORY OF TUNNELING 15 

first. A tunnel at Eriebitz (perhaps the same), on the ''North" 
line, is mentioned in the Fonts et Chaussees Report (above 
cited) as an early Austrian one. In 1856 there were some fifty 
tunnels in Austria of a total length of 13,522 meters. In Italy, 
the Naples-Castelamare line, opened in 1840, had several tun- 
nels. In 1856, the total Italian tunnels amounted to 10,181 
metres; the Bologna-Pistoja line is especially remarkable for its 
semi-subterranean character. Among the early Swiss tunnels, 
especially to be noted is the Hauenstein, commenced in 1853 
and finished in 1858." 

The first railway tunnel in the United States was constructed 
on the Allegheny Portage Railroad in Pennsylvania, between 
1 83 1 and 1833. The tunnel (which was driven through slate) 
was 901 feet long, 25 feet wide by 21 feet high, and was lined 
throughout with masonry 18 inches thick. It was followed by 
the Black Rock tunnel (1835-183 7) on the Philadelphia and 
Reading Railroad, and the Elizabethtown tunnel (183 5- 183 8), 
on what is now the Pennsylvania Railroad; after this time, 
railroad- tunnel construction became so general that by 1850 
as many as forty-eight tunnels had been completed on American 
railways. 

Among the early European mining tunnels driven with gun- 
powder and hand-drilling, mention should be made of the Tiefe 
Georg and the Rothschonberger Stollen in Saxony, the Joseph 
11. Stollen at Schemnitz, Hungary, and the Ernst August Stollen, 
which was later driven under the Tiefe Georg. A number of 
tunnels, of which the Taillades tunnel was the most important, 
were also driven in connection with the Marseilles Aqueduct 
during this period. 

The Tiefe Georg Stollen* was driven between 1777 and 1799. 
The total length of the main tunnel is 34,529 feet; its various 
branches aggregate 25,319 feet more, and yet this immense 
undertaking, driven entirely by hand, was carried out to obtain 
a drainage depth of only 460 feet. It passed through graywacke 
for nearly the entire distance. 

* Drinker, p. 351. 



16 MODERN TUNNELING 

Work was commenced on the Joseph II. Stollen, Schem- 
nitz, Hungary,* in 1782, but owing to various interruptions the 
tunnel was not completed until 1878. The portal is at Wornitz, 
on the left bank of the River Gran, about ten miles west of 
Schemnitz. The tunnel is 10.27 miles long, 9 feet 10 inches high, 
and 5 feet 3 inches in width, and its cost was $4,860,000. It is 
used entirely for mine drainage and the annual saving in pump- 
ing amounts to over $75,000. 

The Rothschonberger StoUen f was driven for the purpose of 
draining the mines of Freiberg, Saxony, and was commenced 
in 1844 and completed April 12, 1877. The tunnel starts in the 
Triebisch Valley at Rothschonberg, about 12 kilometers above 
Meissen on the Elbe. Its length on the line of the original loca- 
tion to Halsbriicke was 42,662 feet, but as completed to a con- 
nection with the Himmelfahrt, including its branches, had a 
total length of 95,149 and a depth below the Anna Stollen of 
308 feet. Hand-drilling and black powder were used down to 
the end of 1875, when Burleigh drills were introduced. The 
work was carried on by the State, and perhaps no better example 
of the inefhciency of governmental control over industrial enter- 
prises could be cited than the record of this work. The tunnel 
was nine feet square and was driven from eighteen headings, 
yet thirty-three years were required for its completion, the 
average rate of progress in each of the headings being only about 
15 feet per month. 

The Ernst August Stollen J was driven below the Tiefe 
Georg Stollen in 1851-1864. The main tunnel is about 34,218 
feet long, but the entire length of the adit and its branches is 
74,452 feet, all driven in rock similar to that in the Georg 
Stollen quoted above. The tunnel is 11 feet high and 5H feet 
wide, driven on a grade of 35.6 feet to the mile. Hand-drilling 
and black powder were used and, working seven-hour shifts, 
the rate of progress was fifty feet per month; four-hour shifts 

* Wochenschrift des Qisterreichischen Ingenieur- und Architekten-Ver- 
eines, 1886, p. 284. 

t Raymond, Trans. A. I. M. E., Vol. VI, pp. 542-558 (1877-1878). 
{ Drinker, p. 351. 



I 




Fig. 3. Starting a tunnel by hand-drilling. 



18 MODERN TUNNELING 

increased the rate of progress to 78.7 feet per month, and by 
crowding the miners to the limit during the last three weeks 
they made 75 feet, or at the rate of 107 feet per month. 

Some idea of the importance the early German miners 
attached to drainage may be gathered from the fact that this 
colossal enterprise only gave them an increased drainage depth 
of 315 feet. 

The Taillades tunnel * on the Marseilles aqueduct was begun 
in January, 1839, and compl'eted at the close of 1846. It was 
driven from fourteen shafts, and in their construction so much 
water was encountered that the work of sinking them was very 
difficult and at times seemed almost impossible. It was finally 
necessary to install at one of the shafts a steam engine of 100 
horse-power in order to remove the water, which amounted to 
3,300 gallons per hour. The cost of sinking the shafts was ap- 
proximately $40 per foot, while the tunnel itself cost approxi- 
mately $37 per foot, or, including the cost of the shafts, $48.50 
per foot. The Assassin tunnel on the same project was some- 
what less difficult and cost but $25.50 per foot for 11,400 feet, 
while the Notre Dame tunnel, which was lined with masonry 
for its entire length of 11,500 feet, cost $32.50 per foot. 

The first large mining tunnel in the United States was com- 
menced as early as 1824. This was the ''Hacklebernie" tunnel 
near Mauch Chunk, Pennsylvania, and it was driven by hand- 
drilling and with black powder. When work on it was stopped 
in 1827, it had penetrated 790 feet through hard conglomerate, 
making an opening 16 feet wide by 8 feet high. Work in it was 
resumed once more in 1846 and the tunnel was extended to a 
length of 2,000 feet. 

The invention of machines to do the work of rock-drilling, 
which occurred almost simultaneously with the discovery of 
high explosives, gave another great impulse to tunnel-driving. 
The first extensive utilization of these aids was in the con- 
struction of the Mt. Cenis tunnel in Europe and the Hoosac 

* "M. de Mont. Richer et le Canal de Marseille." Felix Martin. Paris, 
1878. Gallet et Brand. 



THE HISTORY OF TUNNELING 19 

and Sutro tunnels in this country. The success attained with 
them soon led to further activity in tunneling, not only for rail- 
roads but in connection with mining, drainage, and water supply 
as well — an activity culminating in the immense amount of such 
work undertaken within the last ten or fifteen years. 

The following table gives in chronological order some of the 
more important events connected with these two wonderful 
improvements. 

A SHORT CHRONOLOGICAL HISTORY OF HIGH EXPLOSIVES 
AND ROCK-DRILLS* 

1847. Sobrero discovered nitroglycerine. 

1849. J. J. Couch, of Philadelphia, patented on March 29 the first 

percussion rock-drill. 
1851. J. W. Fowle, of Philadelphia, patented on March 11 the first 

direct-action percussion-drill. 
1854. Schumann invented his percussion-drill at Freiberg. 
1857. Schumann drills used in Freiberg mines. 
1857. Sommeiller invented a rock-drill for use at Mt. Cenis. 
1 86 1. January i, Sommeiller improved drills commenced work in 

the Mt. Cenis tunnel. 
1863. Nobel first applied nitroglycerine as a blasting agent. 

1865. Gun-cotton tried at the Hoosac tunnel by Thomas Doane, 

chief engineer. 

1866. Nitroglycerine tried with great success at the Hoosac tunnel 

by T. P. Shaffner. 
1866- Burleigh drills tried and proved to be a success at the Hoosac 
tunnel. 

1867. Nobel invented dynamite. 

1868. Dynamite patented in America by Nobel. 

MINING AND WATER TUNNELS DRIVEN BY 
MACHINE-DRILLING 

The idea of draining the mines of Virginia City by a deep 
tunnel was first broached in the spring of i860, when Mr. 
Adolph Sutro began negotiations with the mines, the State, and 

* Drinker, pp. 54-55. 



20 



MODERN TUNNELING 



finally with the Federal Government for contracts, concessions, 
etc.. Actual work was first commenced at the portal of the 
tunnel in Carson Valley, three and one-half miles from Dayton, 
on October 19, 1869. The work was carried on by hand until 
September, 1872, when diamond-drilling was begun and experi- 
mented with, more or less unsuccessfully; in 1874, Burleigh 
drills were introduced, operated by compressed air generated in 




Fig. 4. Driving a modern tunnel with machine-drills. 



a compressor made by the Societe John Cockerill, of Seraing, 
Belgium. The tunnel was completed July 18, 1878, when the 
Savage vein was cut 20,000 feet from the portal and 1,922 feet 
below its outcrop. The tunnel, inside of the timbers, was 10 
feet high by 14 feet wide, divided into two passageways by a 
central row of posts. The rate of progress varied greatly, rang- 
ing from 19 to 417 feet per month, the average monthly rate 
from start to finish being 192.3 feet.* 

* Report Commissioners Sutro Tunnel, and Drinker, pp. 337-350. 



THE HISTORY OF TUNNELING 21 

The Tequiquac tunnel, which now forms the most important 
link in the drainage system of the valley of Mexico, was com- 
menced during the reign of the Emperor MaximiHan. The 
work was stopped, however, at the fall of the Empire and was 
not resumed until 1885; ^^^^ then the want of funds prevented 
any material progress until March, 1888. 

This tunnel is six and a quarter miles in length, driven through 
a mass of sand, mud, and soft calcareous sandstone. It is brick- 
lined throughout, the section ovoid, with an extreme width of 
13 feet 9 inches and a height of 14 feet and has a gradient 
of I foot in 1,388. The calculated flow is 450 feet per 
second, or 200,000 gallons per minute. At first the headings 
were driven in the center, but they were soon forced to 
adopt the bottom heading system. The greatest completed 
tunnel advance in any one month was 182 feet and the 
greatest distance that any single heading was driven in a calen- 
dar month was 656 feet. (Trans. Am. Soc. C. E., Vol. XXXII, 
pp. 171-267.) 

The Kelty tunnel on the Glasgow Water Works System is 
2.6 miles in length and 9 feet square. Work was commenced in 
June, 1887, and completed in December, 1889; driving was 
carried on from each portal and both ways from the bottom of 
two shafts. The average rate of progress in each heading was 
4.5 feet per day. The rocks encountered varied from soft shale 
to hard conglomerate. 

The Shoshone tunnel, 1906-19 10, is owned by the Central 
Colorado Power Company, and its intake portal is located on the 
Rio Grande River, twelve miles above Glenwood Springs. It 
is 12,453 f^^t long, 12 feet high, and 16 feet 8 inches wide, and 
is driven for the entire distance through hard metamorphic 
granite. 

Where timber supports were necessary, vertical posts and a 
three-piece arch were employed, all of which were afterward 
completely covered by concrete hning. Driving was carried 
on from seven cross-cut adits, as well as from both intake and 
discharge ends. 



22 MODERN TUNNELING 

Cost of tunnel, not including concrete lining, was $927,653, 
divided as follows: 

Construction costs per linear foot of tunnel: 

Test drifts $ .45 

Drilling and blasting 20 . 66 

Trenching and grading floor 1.15 

Track work 1.76 

Mucking and loading 17.28 

Hauling 2 . 88 

Dumping and maintenance 2.18 

Blasting supplies 8.35 

Drill steel 2.91 

Sharpening and repairing 4 . 60 

Timbering, temporary and permanent 3. 87 

Light and wiring 1.57 

Ventilating 59 

Pipe, air hose, and connections 85 

Power drills 2 . 94 

Hoists and trestles 96 

Pumping 21 

Sundries 28 

Total construction costs $74 . 49 

Overhead costs, including surveying, management, 

office, etc 3091 

Total cost per linear foot $105 . 40 

The Corbett tunnel, of the Shoshone Irrigation Project, 
Wyoming, is approximately 17,000 feet in length, of the inverted 
horseshoe type, having a cross-section about 100 feet in area. 
The tunnel heads opposite the Corbett Station of the Chicago, 
Burlington & Quincy R. R., and its course is parallel to the 
general direction of the Shoshone River, which at three places 
was near enough to permit adits to be excavated from the faces 
of the bluffs to the tunnel, thus affording eight headings for 
construction purposes. The contract for its excavation was 
awarded on September 16, 1905, the price being $33 per linear 
foot. In August, 1906, however, the contractor defaulted after 
having driven 5,219 feet of tunnel, and the work was taken over 



H 



THE HISTORY OF TUNNELING 23 

by the United States Reclamation Service. After doing con- 
siderable retimbering the work was carried on without any 
special difficulties until its completion in 1907. The material 
excavated throughout the tunnel consisted of dry clay, loose 
shales, and stratified sandstones of different degrees of hardness, 
and it decomposed very rapidly upon exposure to the air, thus 
requiring considerable timbering. 

The Big Bend tunnel, owned by the Great Western Power 
Co., is situated at Big Bend on the Feather River in Butte 
County, Cal. The main portion of the tunnel, about three miles 
in length, was driven by the Big Bend Mining Co., from 1883 
to 1887, in order to divert the flow of the river across a narrow 
neck of land and leave the bend dry, allowing the company to 
work the gravels in its bed for gold. This tunnel was enlarged 
from 12 feet high by 13 feet wide to 18 feet high by 14 feet wide, 
and extended 3,400 feet by the present owners in 1 907-1 908. 
The entire tunnel is driven through shale with the exception of 
about 6,000 feet in the middle of the old tunnel, which is in 
diorite. It is lined with concrete about 29 inches thick, with 
an allowable minimum of 6 inches on the arch and 4 inches on 
the invert. 

The Coquitlam tunnel, which is part of the hydro-electric 
power system supplying Vancouver, B. C, and neighboring 
towns, is 12,650 feet long and is driven through solid granite. 
As originally designed it had a mean sectional area of 81 square 
feet. Work of enlarging the tunnel so that it would have a 
sectional area of 176 square feet was begun in November, 1908, 
but was seriously handicapped by the necessity of opening the 
tunnel frequently to maintain the supply of water in a storage 
reservoir, but it was finally completed in March, 191 1. The 
new tunnel is ovoid in cross-section with the point down and is 
unlined. 

The Big Creek tunnel, which is part of the system of the 
Pacific Light and Power Corporation, is 22,000 feet long and 
12 feet in diameter. It was driven from nine adits and two 
portals, has a slope of 3.2 feet per 1,000, and will be used as a 
pressure tunnel throughout, the static pressure at the upper 



24 MODERN TUNNELING 

end being approximately 30 feet and at the lower end approxi- 
mately 100 feet. The formation pierced was solid blue granite 
throughout, except for an occasional faulted zone. These 
were lined with concrete, the aggregate length of such linings 
being 2,000 feet. 

RAILWAY TUNNELS 

While this book is intended to deal chiefly with the con- 
struction of mining tunnels, there is much that can be learned 
from the study of tunnels driven for railroad purposes. Under 
ordinary conditions the rate of progress in a railroad tunnel is 
limited by the speed at which the advance heading can be driven, 
and as these headings do not differ materially from mining 
tunnels, the rates of progress which have been attained in them 
are of great interest to the miner. A railroad- tunnel heading 
must be driven to line and grade the same as a mining tunnel, and 
while it is desirable to maintain a uniform width and height, 
it is not absolutely necessary to do so, thus giving railway- 
tunnel headings a slight advantage over mining tunnels in this 
respect. On the other hand, the multifarious operations carried 
on between the heading and the portal of a railroad tunnel, 
even under the best possible organization, often obstruct tempo- 
rarily transportation to and from the face; the continuity of the 
work is sometimes interfered with by the shooting of the benches 
back of the face; and even where all the holes in the benches 
and headings are blasted together, it takes somewhat longer 
to clear out the smoke from so many groups of shots than it 
would in a mining tunnel from a single round in the heading. 
On the whole, in similar rock and with equally good equipment 
and organization, there should be little if any difference in the 
speed attained in driving a mining- tunnel or a railway tunnel- 
heading, because, although the conditions for rapid progress are 
not exactly identical, the opportunities are practically equal. 
The history of the more important railway tunnels of the world 
also shows forcibly the rapid increase in the rates of driving and 
the lessening of the cost of construction since the introduction 
of rock-drills and high explosives. 



THE HISTORY OF TUNNELING 



25 



PROGRESS AND COST OF 


SOME FAMOUS RAILWAY TUNNELS 




Construction 
Period 


Length, 
Miles 


Duration 
Boring, 
Months 


Avg. Daily 

Progress 

in Headings, 

Feet 


Cost per 
Linear 
Foot 


Mt. Cenis 

Hoosac 

St. Gothard 

Arlberg 


1857-1870 

1858-1874 
1872-1882 
I 880-1 883 
I 898-1 905 
1 906-19 1 1 


7-97 

4-75 
9.26 
6.2 
12.4 
9.3 


157 
... 
88 
40 
78 
54 


6.2 

13-6 
I3.69t 
14.2 t 


$356.00 
398.00 
231.00 
162.30 
239.40 
211.00 


Simplon 

Loetschberg 



* Average east and west headings, 1 865-1 873. 
Allowing only for days on which drilling was carried on, advance was 



7.45 feet per day. 

i Average for last 30 months, 17. 



feet. 



The Mt. Cenis tunnel was driven through the northern spur 
of the Cottic Alps to afford direct connection between the 
French and Italian railway systems. Work was begun on 
August 18, 1857, and the French and Itahan headings met on 
December 25, 1870. The length of the tunnel as completed 
was 42,157 feet and the cost $15,000,000, or $356 per linear 
foot. Its greatest depth below the surface was 5,275 feet, 
where the rock temperature was 85° F. The Sommeiller rock- 
drill, operated by compressed air, was first used in this tunnel 
January 12, 1861, or five years before the introduction of air- 
drills into the Hoosac tunnel in the United States. The rate 
of progress varied greatly with the rock encountered; the total 
time consumed in driving being thirteen years and one month, 
or an average daily progress in each heading of 4.4 feet.§ 

One of the most important early tunnels driven in the United 
States was the Hoosac, on the line of the Troy & Greenfield 
Railway. The project first came under consideration in 1825, 
but actual work was not commenced until 1858. Hand-drilling 
was employed until October 31, 1866, when Burleigh rock-drills 
were first introduced; two months later nitroglycerine was 
substituted for black powder, and the net result of these two most 
important improvements was greatly to increase the rate of 
driving. To be sure, many disheartening delays and interrup- 



§ Drinker, pp. 354-357. Vernon-Harcourt, Pro. Inst. C. E., Vol. XCV, 
pp. 249-261. 



26 MODERN TUNNELING 

tions occurred, due chiefly to failure of the earlier type of drilling 
machines and to change of engineers and contractors, but in 
March, 1869, a contract was let to the Shanly Brothers, of 
Toronto, who completed the work on December 22, 1874. 

The tunnel had a total length of 4^^ miles and was driven 
throughout the greater part of that distance in mica-schist. 
The maximum speed attained in a single heading was 184 feet 
in one month of twenty-six working days, and the average speed 
in the east and west headings for the last six months was 4.2 
feet per day. The cost was $10,000,000, or $398 per linear foot.* 

The great undertaking of driving the St. Gothard tunnel was 
rendered possible through a joint treaty made by Germany, 
France, and Italy, and on May 7, 1872, a contract for the tunnel 
was let to M. Favre, of Genoa, who gave a bond for $1,600,000 
for the successful completion of the work within a period of 
eight years. The tunnel is 48,887 feet, or 9.26 miles, in length, 
driven for the most part through various kinds of schist. After 
testing a number of drills, a final selection was made of Ferroux 
drills for the north side and McKean for the south side. The 
average rate of progress in the headings was 186 feet per month. 
In 1880 one of the headings passed through a zone of softened 
feldspar, which, under the weight of the superincumbent rock, 
squeezed into the tunnel with such force that granite walls and 
arches 6 feet 7 inches in thickness were required to hold it in 
place. The maximum rock temperature encountered was 88° F., 
at a point 5,575 feet below the surface. The headings met 
February 29, 1880, but the tunnel was not completed until 1882, 
nearly two years after the time called for in the original con- 
tract. The total cost was $11,300,000, or $231 per linear foot.f 

The success of the Mt. Cenis and St. Gothard tunnels, coupled 
with the desire of the Austrian Government to have a railway 
route to France which would not pass through Germany or 
Italy, led to the construction of the Arlberg railway, which runs 
from Innsbruck, in the Tyrol, to Bludenz, near the Swiss frontier, 

* Drinker, pp. 315-337- 

t Drinker, pp. 359-370. Vernon-Harcourt, Pro. Inst. C. E., Vol. XCV, 
pp. 261-268. 



I 



THE HISTORY OF TUNNELING 27 

a distance of eighty-five miles, piercing the Arlberg range about 
twenty miles from Bludenz by a tunnel over six miles long. 
In the selection of the machinery and in planning the work, 
advantage was taken of the experience gained in the Mt. Cenis 
and St. Gothard tunnels. In consequence of this, the results 
obtained were as much in advance of the St. Gothard as the 
operations in that tunnel had been an improvement on those 
employed in the ^It. Cenis. The driving of this tunnel was 
commenced in July, 1880, and the headings met on November 
13, 1883. The average rate of progress was thus nearly two 
miles per year. The greatest temperature of the rock was 
64° F. at a point 2,295 ^^^^ below the surface. The Ferroux 
percussion drill, operated by compressed air, was employed in 
the eastern heading, and the Brandt rotary drill, worked by 
water pressure, in the western. The Ferroux drills drove 17,355 
feet and the Brandt drills 14,880 feet, a difference of 2,475 ^^^^ 
in favor of the former. This variation was due more to the 
dissimilarity of the rock in the east and west headings than to 
any difference in the efficiency of the drills themselves, as is 
shown by the following figures, the average daily advance of the 
two drills being as follows: 



Ferroux 


Brandt 


Year 


13-5 ft. 
17.2 " 
17.85 " 


9.5 ft. 
I5.I " 

17.82 " 


In 1881 
In 1882 
In the io>^ months of 1883 



These figures show that as the nature of the rock became 
similar when the faces approached each other, the efficiency of the 
Brandt drill was practically the same as the Ferroux. The 
Brandt drill was much more cheaply operated than the other, 
and it necessitated the use of only seven miners in the heading 
as against twelve with the Ferroux. 

The total length of the tunnel was 32,235 feet and its cost 
was $5,877,684, or $182.30 per linear foot.* 

* Vernon-Harcourt, Pro. Inst. C. E., Vol. XCV, pp. 268-271. Charton, 
"Le Genie Civil," Vol. VI, 1885, pp. 3-18. 



28 MODERN TUNNELING 

The Simplon tunnel consists of two parallel, single-track 
railway tunnels, 56 feet from center to center, driven from 
Brigue, Switzerland, to Iselle, Italy, a distance of 12.4 miles. 

Operations commenced at Brigue November 22, 1898, and 
at Iselle December 21, 1898. The headings met February 24, 
1905, but the tunnel was not completed and ready for use 
until January 25, 1906. Brandt rotary hydraulic drills were 
employed in both headings and the average rate of heading 
advance was 13.69 feet per diem, although when conditions were 
favorable speeds of 16 feet per day in the Itahan end and 20 to 
21 feet in the Swiss end were readily attained. The rock was 
principally gneiss, with occasional beds of slate, granite, and 
marble. 

When operating in hard rock, the cycle of operations was as 
follows : 

Bringing up and adjusting drills 20 minutes 

Drilling i3^-2>2 hours 

Charging and firing 15 minutes 

Mucking 2 .hours 

More serious difficulties were encountered in driving this 
tunnel than any which have yet been undertaken. Swelling 
ground was extremely common, and in places the pressure was 
so great that the roof and sides could only be held in place by 
steel I-beams, with the spaces between rammed with rapid-setting 
concrete. A portion of the tunnel where the pressure was the 
greatest is said to have cost $1,620 per linear foot. Many 
springs were encountered, and the volumes of cold water flowing 
into the tunnel amounted at times to 17,000 gallons per minute. 
Near the center of the tunnel large springs of hot water were 
encountered, amounting in all to 4,330 gallons per minute, one 
spring alone giving 1,400 gallons per minute at 116° F. At 
first it seemed that the high temperatures engendered would 
effectually prevent further advance, but by bringing both cold 
water and cold air into the headings in sufficient volumes, the 
temperature was reduced to a point where it was possible to 
resume work, although it took six months to drive the last 800 




THE HISTORY OF TUNNELING 29 

feet. The rapid average rate of progress maintained in the 
Simplon tunnel, in spite of the difficulties encountered, was due 
to superb equipment and an organization so efficient that 648 
men and 29 horses at the Swiss end and 496 men and 16 horses 
at the Italian end were advantageously employed. 

Notwithstanding the care that was taken in ventilation and 
the precautions adopted for the health and safety of the work- 
men, sixty men were killed during the progress of the work. The 
total cost of tunnel was $15,700,000, or $239.40 per linear foot.* 

The Loetschberg tunnel was driven through the Bernese 
Alps in Switzerland and forms the last link in the railway sys- 
tem connecting the city of Berne with the village of Brigue at 
the north end of the Simplon tunnel. The desirability of con- 
necting the Bernese Oberland with the Rhone Valley was dis- 
cussed as early as 1866 and the present location of the tunnel 
was first proposed in 1889. 

The railway begins at Frutigen in the Bernese Oberland, 
about 32.5 miles from the north portal; 50.5 per cent of this 
length is on horizontal curves. There are about twelve short 
tunnels on the line, aggregating 16,000 feet in length, one of 
which is a spiral tunnel 5,460 feet long, with a 985-foot radius. 
The main tunnel is 47,678 feet long and was first planned to be 
run on a tangent, but a serious cave 1.6 miles from the north 
portal, which killed 25 men and filled up 5,900 feet of tunnel, 
compelled the abandonment of the original fine and the adoption 
of a curved tunnel to pass around the immense, peaty, mud-filled 
fissure which the heading had tapped. 

At the south end IngersoU-Rand air drills and compressors 
were used, while in the north end Myers drills and compressors 
were adopted. Transportation in the tunnel was handled by 
compressed-air locomotives running on 30-inch gauge tracks. 
From four to six drills were employed in each heading, mounted 
on a horizontal bar, which was carried on a carriage, thus neces- 
sitating mucking out after firing before drilling could be com- 
menced in the face. For the last thirty months of driving, the 

* Trans. A. I. M. E., Vol. XLII, pp. 441-446. Fox, Pro. Inst. C. E., 
Vol. CLXXIII, pp. 61-83. 



30 MODERN TUNNELING 

average rate of progress in the south heading was 15.8 feet per 
day, and in the north end, where the driving was much easier, 
18.6. feet per day. On the north side, when the heading was in 
limestone, it was advanced 5,623 feet in six months, or an 
average rate of 30.8 feet per day.* 

The Busk-Ivanhoe tunnel, on the Colorado Midland Railway 
between Leadville and Glenwood Springs, is 9,394 feet long, and 
has an altitude of 10,810 feet at Busk and at Ivanhoe 10,944 feet, 
making it the third highest railway tunnel in the world. It 
is driven almost the entire distance in metamorphic granite 
with some softened shear zones which gave considerable trouble 
in both driving and timbering. The tunnel cost $1,250,000, 
and thirty men were killed in the progress of the work.f 

The Severn tunnel (i 873-1887), which is on the line of the 
Great Western Railway in England, and passes under the estu- 
ary of the Severn River, has a length of 4.35 miles and traverses 
a great variety of strata consisting of conglomerate, limestone, 
carboniferous beds, sandstone, marl, and sand. The most 
serious difhculty encountered in driving was the great volume of 
water coming into the tunnel, not so much from the estuary 
above as from a huge spring on the land side. Several ineffectual 
attempts were made to bulkhead this spring, but before the work 
could be successfully carried on, it was necessary to erect an 
immense pumping plant with a capacity of 45,000 gallons per 
minute, but the maximum amount pumped for any considerable 
period did not exceed 20,000 gallons per minute. { 

The Totley tunnel, on the Dore & Chinley Railway, England, 
is 3.53 miles in length, and is on the line between Sheffield and 
Manchester. Work was commenced in 1888 and the completed 
tunnel was ready for traffic in September, 1893. It is driven 
almost entirely through carbonaceous black shale which con- 
tained some strata of sandstone and grit. The progress of the 
work was greatly impeded by heavy inrushes of water, some- 

* Saunders, Trans. A. I. M. E., Vol. XLII, pp. 446-469. Bonnin, La 
Nature, Paris, 1909, Vol. XXXVII, pp. 147-157. 
'\ Engineering News, August 25, 1872. 
IVernon-Harcourt, Pro. Inst. C. E., Vol. CXXI, pp. 305-308. 



THE HISTORY OF TUNNELING 31 

times carrying vast quantities of sand and silt. For a time the 
discharge from the Padley heading amounted to 5,000 gallons 
per minute. At first the water was carried out of the tunnel 
in 12-inch pipes, but as these proved insufficient and liable to 
clog with sand, the headings were closed up with watertight 
bulkheads and center drains carried in from the portal. This 
work took six weeks, during which time the pressure behind one 
of the dams rose to 155 pounds per square inch.* 

The Aspen tunnel on the Union Pacific Railway between 
Cheyenne and Ogden, although only 5,900 feet in length, is 
interesting on account of the obstacles encountered in driving, 
the difficulty of holding back the swelKng ground, and the fact 
that mechanical loading of the broken rock was successfully 
employed in both headings. The tunnel was driven through 
carbonaceous shale containing an occasional stratum of yellow 
sandstone dipping 20° to 30° to the east, while the course of the 
tunnel was a little south of west. The opening is 22 feet 6 inches 
high and 17 feet wide in the clear, timbered with 12 by 12 -inch 
timbers with vertical posts capped with a seven-segment circular 
arch. These timber sets were spaced 2 feet apart, i foot apart, 
or close together, as the weight of the ground demanded. On 
a portion of the tunnel, walls of soHd 12 by 12-inch timbers 
would not stand the rock pressure, and the timbers were replaced 
by 12-inch steel I beams, which were sometimes buckled side- 
ways before the concrete filling could be rammed in place. 

Small steam shovels of ^-cubic yard bucket capacity, and 
operated by compressed air, were employed for loading cars in 
the headings, and effected a great saving in both time and 
expense.! 

Arthur's Pass tunnel. South Island, New Zealand, sometimes 
known as the Otiro, is on the Kne of the New Zealand Govern- 
ment Railway which connects Christchurch on the east with 
Greymouth on the west coast, and pierces the crest of the South- 
ern Alps for a distance of sH miles. Work began in May, 1898, 
and the contract called for the completion of the work in a 

*Rickard, Pro. Inst. C. E., Vol. CXVI, pp. 1 17-138. 
f Hardesty, Engineering News, March 6, 1902. 



32 



MODERN TUNNELING 



period of five years; price $5,000,000. Tunnel haulage was at 
first attempted with eight- ton benzine locomotives, but they 
were discarded on account of uncertain action and the annoying 
fumes, and electric locomotives were substituted.* 

PARTIAL LIST OF NOTED RAILROAD TUNNELS f 



Name of Tunnel 



Simplon 

St. Gothard 

Loetschberg 

Mont Cenis 

Arlberg 

Ricken 

Tauern 

Ronco 

Tenda 

Hauenstein Base 
Karawanken . . . . 

Somport 

Jungfrau 

Borgallo 

Hoosac 

Severn 

Marianopoli 

Turchino 

Grenchenberg . . . 

Wocheiner 

Mont d'Or 

Albula 

Totley 

Peloritana 

Gravehals 

Puymorens 

Standedge 

Woodhead 

Bosruck 

La Nerthe 

Biblo 

Kaiser Wilhelm. 

Echarneaux 

Blaisy 

Cascade 

Sodbury 



Country 



Switzerland- Italy . 
Switzerland- Italy . 

Switzerland 

France- Italy 

Austria 

Switzerland 

Austria 

Italy 

Italy 

Switzerland 

Austria 

France-Spain 

Switzerland 

Italy. 

United States .... 
England- Wales . . . 

Sicily 

Italy 

Switzerland ...... 

Austria 

France- Switzerl'nd 

Switzerland 

England 

Sicily 

Norway 

France-Spain 

England 

England 

Austria 

France 

Italy 

Germany 

France 

France 

United States. . . . 
England 



Length 



Feet 

65,734 
49,212 

47,685 
42,150 
32,892 
28,230 
28,038 
27,231 
26,568 
26,400 
26,169 
25,656 
23,622 
23,220 

23,175 
23,028 

22,453 
21,150 
21,120 
20,781 
20,025 
19,290 
18,690 
17,898 
17,388 
16,791 
16,020 
15,879 
15,639 
15,303 
13,907 
13,767 
13,620 
13,530 
13,413 
13,299 



Summit level 



Feet 

2,313 

3,788 

4,077 
4,248 
4,300 
650 
4,020 

3,260 

2,088 



1,787 
1,761 

6,133 

2,844 

2,405 



Opened for 
traffic 



1906 

1882 

1913 
1871 
1885 
191O 
1909 
1888 
1899 

X 
1906 

% 

I9I2 

1887 
1876 
1886 

1900 

t 

1909 

X 
1903 

1893 
1885 
1909 

X 

1850 
1845 

1906 



1879 
1895 



[903 



* Gavin, Engineering News, May 9, 19 12. 
t Abstract from The Engineer, November 28, 
additions from other sources. 
I Under construction 1913— 14. 



[913, P- 561—2, with a few 



THE HISTORY OF TUNNELING 



33 



PARTIAL LIST OF NOTED RAILROAD TUNNELS— (Continued) 



Name of Tunnel 



Credo 

Vizzavona 

Khojak 

Suram 

Disley 

Col de St. Michel 

Bramhope 

Festinog ....... 

Cowburn 

Meudon 

Giovo 

Col des Loges . . . 

Cremolina 

Stampede 

Cairasca 

Busk-Ivanhoe. . . 

Caldera 

Hauenstein 

Beacon Hill 

Transandine . . . . 



Country 



France . . . . . 
Corsica . . . . . 
Baluchistan. 
Caucasus. . . 
England. . . . 



France . 

England 

Wales 

England 

France 

Italy 

Switzerland. . . . 

Italy 

United States. . 

Italy 

United States. . 

Peru 

Switzerland. . . . 

China 

Chile- Argentina 



Length 



Feet 
12,960 
12,894 
12,867 
12,810 
11,598 
11,430 
11,262 
11,178 
11,106 
10,962 
10,695 
10,560 

10,514 
9,850 
9,840 

9,394 
9,240 
8,910 
7,212 
6,933 



Summit level 



Feet 

2,791 



890 
200 



944 

775 



10,500 



Opened for 
traffic 



1889 
1892 

1895 
1902 
I901 
1849 
1879 
1893 
1900 



1906 

1893 

19IO 
191I 



The following4s a list of some of the more important Japanese 
tunnels. 

Tsudo adit. Ashio Mine, driven September, 1 88 5-October, 1896, 
II feet high, 13 feet wide, and 10,000 feet long. Located on the 
bank of Watarase River. This tunnel is furnished with double- 
track electric railway, and has seven shafts, each installed with 
electric hoist. The mine contains an aggregate length of more 
than 600,000 feet of levels and winzes. 

Omodani Mine. Ono District. Has five levels, aggregating 58,380 
feet in length; the longest having a length of 12,110 feet, while 
the drainage adit is 10,850 feet long. 

Yoshioka Mine. Kawakami District. Mine opened by eight levels 
and crosscuts, totaling 134,281 feet, the main adit being 39,193 
feet in length. 

Okawamae adit. This adit is for draining the Kusakura Mine, 
Niigataken, and has a length of 10,000 feet. 

Sosuido tunnel* of Sado Mine, Island of Sado, 11,000 feet long. 

Sosuido adit.* This adit is to drain the Innai Silver Mines, and is 
8 feet high, 10 feet wide, and 7,800 feet long. 

Nagara Yama tunnel. (No. if Lake Biwa Canal, near Kyoto.) 

* Sosuido means "Drainage level." 

t There are two Lake Biwa Canals, the first executed in 1886— 1890, and 
the second 1909— 191 1. 



34 MODERN TUNNELING 

Executed in 1886-1890, 14 feet high, 16 feet wide, and 8,040 feet 

long. Rock of slate and sandstone chiefly. 
N agar a Yama tunnel. (No. 2* Lake Biwa Canal, near Kyoto.) 

Executed in 1909-1911, 13^^ feet high, 13 feet wide, and 8,826 

feet long. Rock slate chiefly. 
Kamuriki Railway tunnel. Shinano District. Executed in 1896- 

1900. i6>^ feet high, 15 feet wide, and the length is 8,712 feet. 

Hard rock. 
Kohotoke Railway tunnel. Kai District. (Imperial Government 

R.R.,in line from Tokyo to Kofu.) Executed in 1897-1900, i6>^ 

feet high, 15 feet wide, and 8,356 feet long. Clay rock chiefly. 
Sasago Railway tunnel. Kai District. (Imperial Government R.R. 

in line from Tokyo to Kofu.) Executed in 1896-1902, i6yi feet 

high and 15 feet wide. The length is 15,280 feet, being the 

largest railway tunnel (in one length) completed in Japan. Soft 

rock. 
Ikoma Yama tunnel.^ (Kyoto & Nara Electric Ry.) 17 feet io>^ 

inches high, 22 feet i}4 inches wide, and 11,088 feet long. 
Dokuritsu 2^^% tunnel. Mt. Ari R.R., Formosa. (Just completed.) 

From Kagi Entrance A to Ari Entrance B, three miles, and the 

length of the tunnels in that section i mile and 23 chains and 77 

links. The dimensions of the tunnels are in accordance with the 

regular construction gauge of the Imperial Government Railways. 
Daishi Tsudo. (No. 4 tunnel.) Beshi Copper Mines, lyo District, 

14 feet high, 16 feet wide, and 18,000 feet long. Rock, palaeozoic 

chlorite, and mica schist. 



* There are two Lake Biwa Canals, the first executed in 1 886-1 890, and the 
second 1909-1911. 

t Yama in this table means altitude or mountain. 

I 2^" means the same as Yama, only in Chinese pronunciation. 



CHAPTER III 

MODERN MINING AND WATER TUNNELS 

RESUME OF DATA 

The following paragraphs contain brief descriptions arranged 
alphabetically of tunnels and adits visited in the special field 
work upon which this book is based. In their examination, 
complete information was obtained, wherever possible, concerning 
surface and underground equipment, provisions for the safety of 
the men, the use of explosives, and the methods employed in 
driving, with regard to efficiency, cost, and other similar data 
bearing upon the problem. (See Appendix, page 421.) It is 
impossible, because of lack of space, to reproduce all of this 
some information here, but the following paragraphs convey 
briefly idea as to the main features of the different tunnels. 

Burleigh tunnel: Silver Plume, Colorado. Purpose, mine 
drainage and development. Length, 3,000 feet. Cross-section, 
rectangular, 6 feet wide by 7 feet high. Rock, granite and gneiss. 
Power, steam. Ventilation, exhaust fan, 10- and 12 -inch pipe. 
Drills, Burleigh drills used in 1869 (first use of machine drills 
in an American tunnel) ; Ingersoll-Rand and Leyner drills used 
in driving last 2,800 feet. Mounting, vertical columns. One 
shift per day. Two drillers, two helpers, and three muckers per 
shift. Horse haulage, one-ton cars. Six ty-per- cent gelatine 
dynamite. No timbering. Average monthly progress, 100 feet. 
Approximate cost per hnear foot, S20. Started in 1869 and 
driven 200 feet while testing Burleigh drills; extended later to 
3,000 feet for mine drainage. 

Carter tunnel: Ohio City, Colorado. Purpose, mine drainage 
and transportation. Length, 6,600 feet. Cross-section, rect- 
angular with arched roof, 5.5 feet wide by 7.5 feet high. Rock, 
gneiss. Power, hydraulic and hydro-electric. Ventilation, ex- 
haust blower, lo-inch pipe. Two Leyner drills mounted on ver- 

35 



36 



MODERN TUNNELING 



tical columns. One drilling and two mucking shifts daily. Two 
drillers, one helper, and two muckers per shift. Horse haulage, 
2i-cubic-foot cars. Forty-per-cent and eighty -per-cent gelatine 
dynamite, 8 pounds per cubic yard. One hundred feet timbered. 
Approximate cost per linear foot, $io to $15. Started 1897; on 
November i, 191 1, had driven 6,550 feet; part of intervening 
time spent in drifting along laterals; three years shut down 
entirely, and five years only three men at work. 

Catskill Aqueduct: Ulster, Orange, Putnam, and Westchester 
Counties, and New York City, New York. Length, see list of 
various tunnels on this project given below. Cross-section, see 
Figure 5. This aqueduct includes the following tunnels: 




Fig. 5. Cross-sections of typical tunnels, Catskill Aqueduct. 



Peak: Length, 3,470 feet. Rock, hard. Started, November, 
1908; completed, November, 1909. 

Rondout Siphon: Length, 23,608 feet. Cross-section, circular. 
Rock, Onondaga limestone, Binnewater sandstone, Hudson 
River shale, Esopus shale. High Falls shale, Shawangunk grit, 
Hamilton and Marcellus shale, Helderburg Kmestone. Power, 
steam. Ventilation, exhaust fan, 14- and 20-inch pipe. Four 
Ingersoll-Rand drills in each heading. Mounting, vertical col- 
umn. Two drilling and three mucking shifts per day. Four 
drillers, four helpers, and ten muckers per shift. Mule haulage, 



MODERN MINING AND WATER TUNNELS 37 

40-cubic-foot cars. Sixty-per-cent gelatine dynamite, 4 to 5 
pounds per cubic yard of heading. Lined with concrete. Aver- 
age monthly progress per heading, 220 feet. Started, March, 
1909; completed. May, 191 1. 

Bonticou: Length, 6,823 feet. Cross-section, horseshoe. 
Rock, Hudson River shale. Started, November, 1908; com- 
pleted, February, 191 1. 

W allkill Siphon: Length, 23,391 feet. Cross-section, circular. 
Rock, Hudson River shale. Power, electricity, purchased. 
Ventilation, fan, 12- and 14-inch pipe. Four Ingersoll-Rand or 
SulKvan drills in each heading. Mounting, vertical column. 
Three shifts per day. Four drillers, four helpers, and eight 
muckers per shift. Electric haulage, 40-cubic-foot cars. Sixty- 
per-cent gelatine dynamite, 4.3 to 4.6 pounds per cubic yard of 
heading. Lined with concrete. Average monthly progress per 
heading, 300 feet. Started, October, 1909; completed, Decem- 
ber, 1910. 

Moodna Siphon: Length, 25,200 feet. Cross-section, circular. 
Rock, hard sandstone, granite, and Hudson River shale. Power, 
steam. Ventilation, jet of compressed air in 12-inch pipe. Four 
Ingersoll-Rand drills per heading. Mounting, vertical column. 
Three shifts per day. Four drillers, four helpers, and ten 
muckers per shift. Mule haulage, 40-cubic-foot cars. Seventy- 
five-per-cent gelatine dynamite. Lined with concrete. Average 
monthly progress per heading, 165 feet. Started, February, 
1 9 10; completed, June, 191 1. 

Hudson Siphon: 1,100 feet below sea level. Length, 3,022 
feet. Rock, granite. Started, December, 19 10; completed, 
January, 191 2. 

Breakneck: Length, 1,054 feet. Cross-section, horseshoe. 
Rock, granite and gneiss. Started, December, 19 10; com- 
pleted, April, 191 1. 

Bull Hill: Length, 5,365 feet. Rock, granite. Started, June, 
1909; completed, January, 1911. 

Garrison: Length, 11,430 feet. Rock, hard gneiss. Started, 
June, 1907; suspended, November, 19 10, to April, 19 11; com- 
pleted, 191 2. 



38 MODERN TUNNELING 

Hunters Brook: Length, 6,150 feet. Cross-section, horseshoe. 
Rock, schist of variable hardness. Started, September, 1909; 
completed, 191 2. 

Turkey Mountain: Length, 1,400 feet. Rock, Manhattan 
schist. Started^ October, 1909; completed, December, 1910. 

Croton Lake: Length, 2,639 ^^^t. Rock, Manhattan schist and 
Fordham gneiss. Started, July, 19 10; completed, January, 191 2. 

Croton: Length, 3,000 feet. Rock, Manhattan schist. Started, 
August, 1909; completed, December, 1911. 

Chadeayin: Length, 700 feet. Rock, Manhattan schist. 
Started, November, 1909; completed, September, 19 10. 

Millwood: Length, 4,750 feet. Rock, hard gneiss. Started, 
May, 1 9 10; completed, 191 2. 

Sarles: Length, 5,230 feet. Rock, hard gneiss and schist. 
Started, February, 1910; completed, 1912. 

Harlem Railroad: Length, 1,100 feet. Rock, hard gneiss and 
schist. Started, June, 19 10; completed, January, 191 1. 

Reynolds Hill: Length, 3,650 feet. Rock, schist. Started, 
October, 19 10; completed, 191 2. 

East View: Length, 5,388 feet. Rock, schist. Started, 
April, 1 910; completed, January, 191 2. 

Elmsford: Length, 2,375 f^^t. Rock, soft schist. Started, 
May, 1911; completed, 191 2. 

Yonkers Siphon: Length, 12,302 feet. Cross-section, circular. 
Rock, Yonkers gneiss and granite. Power, electrical. No 
ventilation supplied, except by opening compressed-air line. 
Four Ingersoll-Rand drills in each heading. Mounting, vertical 
columns. Two drilling shifts and three mucking shifts per day. 
Four drillers, four helpers, and eight to twelve muckers per 
shift. Mule haulage, 40-cubic-foot cars. Sixty-per-cent gelatine 
dynamite, 4 to 5 pounds per cubic yard of heading. Lined 
with concrete. Average monthly progress per heading, 155 
feet. Started, July, 1910; completed, July, 191 1. 

Van Cortlandt Siphon: Length, 1,809 feet. Rock, Yonkers 
gneiss. Started, July, 19 10; completed, September, 191 1. 

City tunnel: Length, 18. 11 miles. Rock, Fordham gneiss 
and Manhattan schist. Started, December, 191 1; completed, 1914. 



MODERN MINING AND WATER TUNNELS 39 

Central tunnel: Idaho Springs, Colorado. Purpose, mine 
drainage and transportation. Length, 9,000 feet. Cross-section, 
rectangular. Two thousand five hundred feet driven 12 
feet wide by 8 feet high; the remainder 5 feet wide by 7 feet 
high. Rock, Idaho Springs gneiss. Power, steam. Ventila- 
tion, exhaust with blower through 19-inch pipe. Two Leyner 
drills in the heading. Mounting, horizontal bar. One shift per 
day. Two drillers, two helpers, and four muckers per shift. 
Horse haulage, 30-cubic-foot cars. Forty-per-cent gelatine 
dynamite, 5 to 7 pounds per cubic yard of heading. One hundred 
feet timbered. Average monthly progress in the heading, 200 
feet. 

Coronado tunnel: Metcalf, Arizona. Purpose, mine develop- 
ment and transportation. Length, 6,300 feet. Cross-section, 
square, 9 by 9 feet. Rock, granite and porphyry. Power, steam 
with crude oil as fuel. Ventilation, blow and exhaust with 
pressure blower through a 12-inch pipe. Ingersoll-Rand and 
Sullivan drills were used in the first half of the tunnel, Leyner- 
Ingersoll drills were used in the last half. Three shifts per 
day. Two and three drillers, one helper, and four to six muckers 
per shift. Mule haulage, '* one-ton" cars. Sixty-per-cent and 
loo-per-cent gelatine dynamite. Average monthly progress, 
415 feet. Average cost per linear foot, $22.64. (See page 329.) 
Started, June, 191 2; completed, August, 1913. 

Gold Links tunnel: Ohio City, Colorado. Purpose, mine 
drainage and transportation. Length, 3,900 feet. Cross-section, 
rectangular with arched roof, 6 feet wide by 8 feet high. Rock, 
gneiss, intruded granite, porphyry. Ventilation, exhaust with 
fan through 15-inch pipe. One Ingersoll-Rand drill. Mounting, 
vertical column. Two shifts per day. One driller, one helper, 
and two or three muckers per shift. Horse haulage, 25-cubic- 
foot cars. Forty-per-cent gelatine dynamite, 5 to 6 pounds per 
cubic yard of heading. Two hundred feet timbered. Average 
monthly progress, 200 feet. Approximate cost per linear foot, 
not including permanent equipment, $19. Started, May, 1906; 
driven intermittently; completed, December, 191 2. 

Gunnison tunnel: Montrose, Colorado. Purpose, irrigation. 



40 MODERN TUNNELING 

Length, 30,645 feet. Cross-section, horseshoe, 10 feet wide, 12.5 
feet high. Rock, chiefly metamorphosed granite, with som_e 
water-bearing clay and gravel, some hard black shale, and a 
zone of faulted and broken material. Power, steam. Ventila- 
tion, blow and exhaust with blower through 15-inch pipe. Four 
Sullivan drills per heading (Leyner drills also tried). Mounting, 
vertical column for SulHvan drills; horizontal bar for Leyner 
drills. Three shifts per day. Four drillers, four helpers, and 
five to eight muckers per shift. Electric haulage, 35- and 54- 
cubic-foot cars. Sixty- and 40-per-cent gelatine dynamite. 
5.5 pounds per cubic yard of heading. Fourteen thousand five 
hundred feet timbered. Average monthly progress per heading, 
250 feet. Cost per Hnear foot of tunnel, $70.66. Started, 
January, 1905; completed, July, 1909. 

Laramie-Poudre tunnel: Larimer County, Colorado. Purpose, 
irrigation. Length, 11,300 feet. Cross-section, rectangular, 
9.5 feet wide by 7.5 feet high. Rock, close-grained granite. 
Power, hydraulic and hydro-electric. Ventilation, exhaust 
with blower through 14-inch and 15-inch pipe. Three Leyner 
drills in the heading. Mounting, horizontal bar. Three shifts 
per day. Three drillers, two helpers, and six muckers per shift. 
Mule haulage, i6-cubic-foot cars. Sixty- and loo-per-cent. 
gelatine dynamite, 3.9 to 4.9 pounds per cubic yard of heading. 
Six hundred and thirty feet timbered. Average monthly 
progress per heading, 509 feet. Cost per linear foot of tunnel, 
$39.54. Started, December, 1909; completed, July, 191 1. 

Lausanne tunnel: Mauch Chunk, Pennsylvania. Purpose, 
mine drainage. Length, 20,000 feet. Cross-section, arched 
roof, 12 feet wide by 8 feet high. Rock, shale, conglomerate, 
slate, and anthracite coal. Power, steam. Ventilation, blow 
with fan through two 16-inch pipes. Two Ingersoll-Rand 
drills in the heading. Mounting, vertical columns. Three 
shifts per day. Two drillers, two helpers, and four to five 
muckers per shift. Electric haulage, 78-cubic-foot cars. Sixty- 
per-cent gelatine dynamite. Average monthly progress per 
heading, 340 feet. Cost per linear foot of tunnel, $19. Started, 
July, 1906; completed, February, 191 2. 



MODERN MINING AND WATER TUNNELS 



41 



Los Angeles Aqueduct: Location, Inyo, Kern, and Los Angeles 
Counties, California. Purpose, water supply, power, and irriga- 
tion. Cross-section, see Figure 6. 




Fig, 6. Cross-sections of typical tunnels, Los Angeles Aqueduct. 

Little Lake and Grapevine Divisions: Power, electricity, pur- 
chased from separate plant owned by the Aqueduct. Ventila- 



42 MODERN TUNNELING 

tion, blow and exhaust with pressure blower through 12-inch 
pipe. Two Leyner drills per heading. Mounting, horizontal 
bar. One and two shifts on Little Lake Division; two shifts 
per day on Grapevine Division. Two drillers, two helpers, and 
five muckers per shift. Mule and electric haulage on Little 
Lake Division; electric haulage on Grapevine Division, 32-cubic- 
foot cars both Divisions. Forty-per-cent gelatine dynamite, 
4/^ pounds per cubic yard of heading. Grapevine Division; 
14,745 feet timbered on Little Lake Division; 1,500 feet 
timbered on Grapevine Division. Started, 1909; completed, 

1913- 

Tunnel iB: Length, 1,918 feet. Rock, medium granite. 
Started, June, 1909; completed, December, 1909. 

Tunnel 2: Length, 1,739 feet. Rock, medium granite, very 
wet. Started, May, 1909; completed, September, 1909. 

Tunnel 2 A: Length, 1,322 feet. Rock, medium granite. 
Started, May, 1909; completed, September, 1909. 

Tunnel j: Length, 4,044 feet. Rock, north heading, medium 
granite; south heading, variable granite, with pockets of CO2 
gas. Started, March, 1909; completed, July, 191 1. 

Tunnel 4: Length, 2,033 ^^^t. Rock, medium to hard granite. 
Started, February, 1909; completed, November, 1909. 

Tunnel 5; Length, 1,178 feet. Rock, medium to hard granite. 
Started, February, 1909; completed, July, 1909. 

Tunnel 6: Length, 411 feet. Rock, medium granite. Started, 
February, 1909; completed. May, 1909. 

Tunnel y: Length, 3,596 feet. Rock, variable, soft, and 
swelling in parts. Started, March, 1909; completed, July, 
1911. 

Tunnel 8: Length, 2,560 feet. Rock, medium to hard, swelling 
in parts. Started, November, 1909; completed, August, 191 1. 

Tunnel g: Length, 3,506 feet. Rock, medium to hard granite. 
Started, November, 1909; completed, February, 191 1. 

Tunnel 10: Length, 5,755 feet. Rock, medium granite. 
Started, December, 1909; completed, August, 191 1. 

Tunnel 10 A: Length, 5,961 feet. Rock, medium to hard 
granite. Started, March, 19 10; completed, December, 191 1. 



4 



modern mining and water tunnels 43 

Grapevine Division: 

Tunnel 12: Length, 4,900 feet. Rock, hard granite. Started, 
July, 1909; completed, May, 191 1. 

Tunnel ij: Length, 1,958 feet. Rock, hard granite. Started, 
May, 1909; completed, April, 1910. 

Tunnel 14: Length, 859 feet. Rock, hard granite. Started, 
April, 1909; completed, February, 19 10. 

Tunnel 15: Length, 895 feet. Rock, hard granite. Started, 
May, 1909; completed, December, 1909. 

Tunnel 16: Length, 2,723 feet. Rock, hard granite. Started, 
April, 1909; completed, February, 19 10. 

Tw/zwe/ 17; Length, 3,022 feet. Rock, hard granite. Started, 
March, 1909; completed, November, 19 10. 

r^ww^/ 17/2.* Length, 1,364 feet. Rock, hard granite. Started, 
January, 19 10; completed, November, 19 10. 

Tunnel 17 A: Length, 5,330 feet. Rock, hard granite. Started, 
January, 19 10; completed, February, 191 2. 

Tunnel ly B: Length, 9,220 feet. Started, March, 1910; 
completed, 191 2. 
Elizabeth Lake Division: 

Elizabeth Lake tunnel: Length, 26,860 feet. Cross-section, 
rectangular with arched roof, 12.3 feet high by 12.75 feet wide. 
Rock, medium to hard granite. Power, electricity. Ventilation, 
blow and exhaust with blower through 18-inch pipe. Three 
Leyner drills in each heading. Mounting, horizontal bar. Three 
shifts per day. Three drillers, three helpers, and nine muckers 
per shift. Electric haulage, 32-cubic-foot cars. Forty-per-cent 
gelatine dynamite, 5 to 6 pounds per cubic yard of heading. 
Sixteen thousand four hundred feet timbered. Average monthly 
progress per heading, 350 feet. Cost per linear foot of tunnel, 
$40.50. Started, October, 1907; completed, February, 191 1. 

Lucania tunnel: Idaho Springs, Colorado. Purpose, mine 
development and transportation. Length, 6,385 feet. Cross- 
section, 8 feet square. Rock, hard granite. Power, purchased 
electricity. Ventilation, exhaust with blower through 18-inch 
and 19-inch pipe. Three Leyner drills in the heading. Mount- 



44 MODERN TUNNELING 

ing, vertical column. One shift per day. Three drillers, two 
helpers, and three muckers per shift. Horse haulage, 22-cubic- 
foot cars. Fifty-per-cent gelatine dynamite, 8 to 9 pounds per 
cubic yard of heading. No timbering. Average monthly prog- 
ress, 125 feet. Cost per linear foot of tunnel, $23.06. Started, 
1 901; driven intermittently; completed, 191 1. 

Marshall-Russell tunnel: Empire, Colorado. Purpose, mine 
drainage, development, mining, and transportation. Length, 
6,400 feet. Cross-section, rectangular, 8 feet wide by 9 feet high. 
Rock, granite and gneiss. Power, purchased electricity with 
auxiliary hydraulic plant. Ventilation, exhaust with fan through 
12-inch and 13-inch pipe. Two Leyner drills in the heading. 
Mounting, vertical column. One shift per day. Two drillers, 
two helpers, and four muckers per shift. Horse haulage, 28- and 
25-cubic-foot cars. Forty- and 80-per-cent gelatine dynamite. 
One hundred and fifty feet timbered. Average monthly progress, 
160 feet. Cost per linear foot of tunnel, $18.88. Started, 1901; 
driven intermittently; completed, 191 1. 

Mission tunnel: Santa Barbara, CaHfornia. Purpose, water 
supply. Length, 19,560 feet. Cross-section, trapezoid, 4.5 feet 
wide at the top, 6 feet wide at the base, and 7 feet high. Rock, 
shale, slate, and hard sandstone. Power, purchased electricity. 
Ventilation, blow and exhaust with blower through lo-inch pipe. 
One Leyner drill in the heading. Mounting, horizontal bar. 
Three shifts per day. One driller, one helper, and four muckers 
per shift. Electrical haulage, 22-cubic-foot cars. Forty- and 
60-per-cent gelatine dynamite, 6 to 8 pounds per cubic yard of 
heading. Five hundred and sixty feet timbered. Average 
monthly progress, 210 feet. Cost per linear foot of tunnel, $19.91. 
Completed, 191 2. 

Newhouse tunnel: Idaho Springs, Colorado. Purpose, drain- 
age and transportation. Length, 22,000 feet. Cross-section, 8 
feet square. Rock, Idaho Springs gneiss. Power, purchased 
electricity. A^entilation, exhaust with pressure blower through 
18-inch pipe. Two and three Leyner drills in the heading. 
Mounting, horizontal bar and vertical column at different times. 
One and two drill shifts per day. Two and three drillers, two 



MODERN MINING AND WATER TUNNELS 45 

helpers, and three muckers per shift. Electric haulage, 57- and 
35-cubic-foot cars. Forty- and loo-per-cent gelatine dynamite. 
One thousand feet timbered. Started, 1893; driven intermit- 
tently; completed, November, 19 10. 

Nisqually tunnel: Alder, Washington. Purpose, hydro- 
electric power for City of Tacoma. Length, 10,000 feet. Cross- 
section, rectangular with arched roof, 9^ feet wide by 11 feet 
high. Rock, rhyolite. Power, hydraulic and hydro-electric. 
Ventilation, exhaust w^ith fan through 14-inch pipe. Two 
Ingersoll-Rand drills at the headworks end, two Leyner drills at 
the discharge end. Mounting, horizontal bar. Two drilKng 
shifts and three mucking shifts per day. Two drillers, two help- 
ers, and four muckers per shift. Electric haulage, 27-cubic-foot 
cars. Forty-per-cent gelatine dynamite. Practically no timber- 
ing. Average monthly progress per heading, 300 feet. Approxi- 
mate cost per linear foot of tunnel, not including permanent 
equipment, S15 to $20. Started, 1910; completed, 1912. 

Ontario tunnel: Park City, Utah. Purpose, mine drainage. 
Length, 24,000 fe^t. Cross-section, trapezoid, 5 feet wide at the 
base, 4 feet wide at the top, 7>^ feet high. Rock, porphyry, 
granite, quartzite, and limestone. Started, July 25, 1908; sus- 
pended for several periods of from one to fourteen months; still 
unfinished. 

Rawley tunnel: Bonanza, Colorado. Purpose, mine drainage 
and development. Length, 6,235 feet. Cross-section, trapezoid, 
8 feet wide at the base, 7 feet wdde at the top, 7 feet high. Rock, 
andesite. Power, steam, wood fuel. Ventilation, exhaust with 
pressure blower through 12 -inch and 13 -inch pipe. Two Leyner 
drills in the heading. Mounting, horizontal bar. Two and three 
shifts per day. Two drillers, two helpers, and three muckers per 
shift. Horse haulage, 17-cubic-foot cars. Forty- and 6o-per-cent 
gelatine dynamite, 6 pounds per cubic yard of heading. One 
thousand six hundred and eighteen feet timbered. Average 
monthly progress, 350 feet. Cost per linear foot of tunnel, 
$19.88. Started, May, 1911; completed, October, 1912. 

Raymond tunnel: Ohio City, Colorado. Purpose, mine drain- 
age and development. Length, 3,200 feet. Cross-section, 9 feet 



\ 



46 



MODERN TUNNELING 



square. Rock, granite and gneiss. Power, steam. Ventilation, 
blow and exhaust with blower through 14-inch pipe: Three 
Leyner drills in the heading. Mounting, horizontal bar. One 
shift per day. Three drillers, two helpers, and two to three 
muckers per shift. Horse haulage, 32-cubic-foot cars. Forty- 
and 60-per-cent gelatine dynamite, 3 to 4 pounds per cubic yard 
of heading. One hundred feet timbered. Average monthly 




Fig. 7. Cross-section, Roosevelt Tunnel. 



progress, 200 feet. Approximate cost per linear foot of tunnel, 
$15. Started, 1903; driven intermittently; completed, 191 2. 
Roosevelt tunnel: Cripple Creek, Colorado. Purpose, mine 
drainage. Length, 15,700 feet. Cross-section, see Figure 7. 
Rock, Pike's Peak granite. Power, purchased electricity. Ven- 
tilation, exhaust with pressure blower through 16-inch and 17- 
inch pipe. Two and three Leyner drills in the heading. Mount- 
ing, horizontal bar. Three shifts per day. Three drillers, two 
helpers, and four muckers per shift. Mule haulage, i6-cubic- 
foot cars. Sixty- and loo-per-cent gelatine dynamite. No tim- 
bering. Average monthly progress per heading, 285 feet. Cost 
per linear foot of tunnel, $27.27. Started, February, 1908; com- 
pleted, November, 19 10. 



MODERN MINING AND WATER TUNNELS 47 

Shepard^s Pass tunnel: Oakland, California. Purpose, elec- 
tric railway. Length, 3,000 feet. Rock, shale. Power, elec- 
tricity. Ventilation, fan. Three or four Ingersoll-Rand drills 
per heading. Horizontal bar mounting. One shift per day. 
Three to four drillers and helpers, four to six muckers (per head- 
ing) per shift. Electric haulage. Forty-per-cent gelatine 
dynamite. All timbered, ground very heavy. Average 
monthly progress, 160 to 175 feet. Started, 1911; completed, 

1913- 

Siwatch tunnel: Leadville, Colorado. Purpose, development. 
Length, 5,000 feet. Cross-section, rectangular, 6 feet wide by 
7.5 feet high. Rock, granite. Power, purchased electricity. Ven- 
tilation, exhaust with pressure blower through lo-inch pipe. 
Two Waugh stoping drills in the heading. Mounting, horizontal 
bar. Two shifts per day. Two drillers, no helpers, and two to 
three muckers per shift. Electric haulage, 33-cubic-foot cars. 
Forty-per-cent gelatine dynamite. Six hundred feet timbered. 
Driven intermittently; not yet completed. 

Snake Creek tunnel: Heber, Utah. Purpose, mine drainage 
and development. Length, 14,000 feet. Cross-section, rectan- 
gular, 9.5 feet wide by 6.5 feet high. Rock, diabase. Power, 
purchased electricity. Ventilation, exhaust with pressure blower 
through 16-inch pipe. Two SulHvan drills in the heading. 
Mounting, horizontal bar. Two shifts per day. Two drillers, 
two helpers, and three muckers per shift. Horse haulage, 20- 
cubic-foot cars. Forty- and 60-per-cent gelatine dynamite, 7 
pounds per cubic yard of heading. Three hundred and fifty 
feet timbered. Average monthly progress, 250 feet. Started, 
May, 1 9 10; driven intermittently; not yet completed. 

Stilwell tunnel: Telluride, Colorado. Purpose, mine dramage 
and development. Length, 2,600 feet. Cross-section, 7 feet" 
square. Rock, conglomerate and andesite. Power, purchased 
electricity. Ventilation, exhaust with fan through lo-inch pipe. 
Two Ingersoll-Sergeant drills in the heading. Mounting, vertical 
column. One shift per day. Two drillers, two helpers, and three 
muckers per shift. Horse haulage, 22-cubic-foot cars. Forty-per- 
cent gelatine dynamite, 8 to 10 pounds per cubic yard of heading. 



48 MODERN TUNNELING 

No timbering. Average monthly progress, 150 feet. Cost per 
linear foot of tunnel, $23.38. Started, 1901; driven intermit- 
tently; completed, 1906. 

Strawberry tunnel: Wasatch County, Utah. Purpose, irri- 
gation. Length, 19,100 feet. Cross-section, arched roof, 8 feet 
wide, gyi feet high. Rock, shale and sandstone. Power, elec- 
tric. Ventilation, exhaust with pressure blower through 14-inch 
pipe. Two Sullivan drills in the heading. Mounting, vertical 
column. Three shifts per day. Two drillers, two helpers, and 
six muckers per shift. Electric haulage, 47-cubic-foot cars. 
Forty-per-cent gelatine dynamite, 5 to 6 pounds per cubic yard 
heading. Two thousand five hundred feet timbered. Average 
monthly progress, 300 feet. Cost per linear foot of tunnel, $36.78. 
Started, 1906; completed, 191 2. 

Utah Metals tunnel: Tooele, Utah. Purpose, transportation. 
Length, 11,780 feet. Cross-section, rectangular, 10 feet wide by 
8 feet high. Rock, quartzite. Power, hydrauHc. Ventilation, 
exhaust with fan through 12-inch pipe. Two Ingersoll-Rand 
drills in the heading. Mounting, horizontal bar. Two shifts per 
day. Two drillers, two helpers, and four muckers per shift. 
Electric haulage, 32-cubic-foot cars. Forty- and 60-per-cent gel- 
atine dynamite, 4 to 5 pounds per cubic yard of heading. Five 
hundred feet timbered. Average monthly progress, 250 feet. 
Approximate cost per linear foot of tunnel, $15. Started, 1906; 
driven intermittently; not yet completed. 

Yak tunnel: Leadville, Colorado. Purpose, transportation 
and development. Length, 23,800 feet. Cross-section, 7 feet 
square. Rock, sandstone, limestone, shale, porphyry, and 
granite. Power, electric. No ventilation supplied, except by 
opening compressed-air line. Two Ingersoll-Rand drills in the 
' heading. Mounting, horizontal bar. Three shifts per day. Two 
drillers, two helpers, and two muckers per shift. Electric haul- 
age, 30-cubic-foot cars. Forty per cent, gelatine dynamite, 4 to 
5 pounds per cubic yard of heading. Eight thousand feet tim- 
bered. Average monthly progress, 200 feet. Approximate cost 
per linear foot of tunnel, $20. Started, 1886; driven intermit- 
tently; completed, 19 10. 



MODERN MINING AND WATER TUNNELS 49 

MODERN TUNNELS DESCRIBED IN ENGINEERING 
MAGAZINES 

The following tables are comparable with those above, and 
give practically similar information concerning certain tunnels 
which were not examined in the field, but which are quite fully- 
described in engineering periodicals. Although the information 
contained in these various accounts is, perhaps, somewhat 
less complete than similar data obtained at other tunnels 
actually visited, nevertheless it is generally sufficient in each 
case to convey a good idea of the main features of the 
work done. 

Bufalo Water Works tunnel: Buffalo, New York. Purpose, 
water supply. Length, 6,575 f^^t. Cross-section, nearly rect- 
angular, 15 feet wide by 15K feet high. Rock, limestone. Power, 
steam. Ventilation, tunnel driven under compressed air, no ven- 
tilation used. Four Ingersoll-Sergeant drills in the heading. 
Mounting, vertical column. Three shifts per day. Four drillers, 
four helpers, and ten muckers per shift. Electric haulage, 27- 
cubic-foot cars. Sixty-per-cent gelatine dynamite, 4.8 pounds 
per cubic yard of heading. Average monthly progress, 235 feet. 
Started, July, 1907; completed, April, 1910. Reference, Engin- 
eering Record, June 25, 19 10, page 802. 

Chipeta adit: Ouray, Colorado. Purpose, mine development. 
Length, 2,000 feet. Cross-section, 7.5 feet square. Power, steam. 
No ventilation supphed except by opening compressed-air line. 
Two Ingersoll-Rand drills in the heading. Mounting, horizontal 
bar. Two shifts per day. Two drillers, one helper, and four 
muckers per shift. Mule haulage, 20-cubic-foot cars. Five to 6 
pounds of explosive per cubic yard of heading. One hundred and 
fifteen feet timbered. Average monthly progress per heading, 
340 feet. Approximate cost per linear foot of tunnel, not includ- 
ing permanent equipment, $12. Started, August, 1907; com- 
pleted, March, 1908. Reference, Alining and Scientific Press ^ 
July II, 1908, page 60. 

Cornelius Gap tunnel: Near Portland, Oregon. Purpose, elec- 
tric railway. Cross-section, arched roof, 17.5 feet wide by 22.5 



50 MODERN TUNNELING 

feet high. Length, 4,100 feet. Rock, basalt. Reference, Engi- 
neering News, June 29, 191 1, page 783. 

Fort Williams Water tunnel: Fort Williams, Ontario. Pur- 
pose, water supply. Length, 4,820 feet. Cross-section, rectan- 
gular with arched roof, 5 feet wide, 6.5 feet high. Rock, basalt. 
Power, electric. Ventilation, blow with fan through 15-inch 
pipe. One Ingersoll-Rand drill in heading. Mounting, vertical 
column. Two and three shifts per day. One driller, one helper, 
and three muckers per shift. Eighteen-cubic-foot cars. Forty- 
per cent, gelatine dynamite, 5 to 10 pounds per cubic yard of 
heading. Lined with concrete. Average monthly progress per 
heading, 85 feet. Cost per linear foot of tunnel, $27.89. Started, 
May, 1907; completed. May, 1909. Reference, Engineering and 
Contracting, May 25, 1910, page 472. 

Grand Central tunnel: New York City. Purpose, sewer. 
Length, 3,000 feet. Cross-section, circular, 8 feet in diameter. 
Rock, gneiss. No ventilation suppKed, except by opening com- 
pressed-air line. Two and three Ingersoll-Rand and Sullivan 
drills in the heading. Mounting, vertical column. One shift per 
day. Two and three drillers, two and three helpers, and two 
muckers per shift. Used a >^-cubic-foot bucket on a flat car. 
•Started, 1907; completed, 1908. Keierence, Engineering Record, 
April II, 1908, page 496. 

Joker tunnel: Red Mountain, Colorado. Purpose, mine drain- 
age and development. Length, 5,055 feet. Cross-section, rect- 
angular, 12 feet wide, 11 feet high. Power, steam. Ventilation, 
exhaust with fan through 15-inch pipe. Two and three Leyner 
drills in the heading. Mounting, vertical column. One drill 
shift and two mucking shifts per day. Two and three drillers, 
two helpers, and four muckers per shift. Mule haulage, 30-cubic- 
foot cars. Practically all timbered. Average monthly progress, 
215 feet. Completed, 1907. Reference, Mines and Minerals , 
May, 1907, page 470. 

Kellogg tunnel: Wardner, Idaho. Purpose, mine development. 
Length, 9,000 feet. Cross-section, arched roof, 9 feet wide and 
1 1 feet high. Rock, quartzite. Reference, Mines and Minerals , 
October, 1901, page 122. 



I 



MODERN MINING AND WATER TUNNELS 51 

Mount Royal tunnel: Montreal, Canada. Purpose, railroad. 
Length, 3.25 miles. Cross-section, rectangular with arched roof, 
during construction 30.5 feet wide and 21.25 f^^t high, when 
completed will be twin tubes each 13.5 feet wide and 14 feet high, 
separated by an 18-inch wall of concrete. Rock, limestone and 
volcanic breccia. Power, purchased electricity. Ventilation, 
pressure blower. Three or four Sullivan water drills per heading. 
Mounting, horizontal bar and special drill carriage. Three shifts 
per day; four drillers, four helpers, and six muckers per shift. 
Electric haulage. Sixty-per-cent gelatine dynamite. Average 
progress in No. i heading, first eight months, 351 feet. Refer- 
ences, Engineering and Mining Journal, July 26, 1913, pages 
147-49; Mine and Quarry, August 1913, pages 730-39. 

Northwest Water tunnel: Chicago, Illinois. Purpose, water 
supply. Length, 21,180 feet. Cross-section, horseshoe, area 
equivalent to 14-foot circle. Rock, limestone. No ventilation 
supplied, except by opening compressed-air line. Four Ingersoll- 
Rand drills in the heading. Mounting, vertical column. Two 
shifts per day. Four drillers, four helpers, and six muckers per 
shift. Mule haulage, 22-cubic-foot cars. Average monthly 
progress per heading, 400 feet. Reference, Engineering Record, 
August 7, 1909, page 144. 

Ophelia tunnel: Cripple Creek, Colorado. Purpose, mine 
drainage and development. Length, 8,500 feet. Cross-section, 
9 feet square. Rock, granite and breccia. Power, steam. Ven- 
tilation, blow with pressure blower through 15-inch pipe. Two 
Sulhvan drills in the heading. Mounting, vertical column. 
Three shifts per day. Two drillers, two helpers, and three 
muckers per shift. Compressed air haulage. Average monthly 
progress, 350 feet. Started, 1905; completed, 1907. Reference, 
Mine and Quarry, May, 1907, page 118. 

Roger^s Pass tunnel: Between Ross Peak and Beaver Mouth, 
British Columbia. Purpose, railroad. Length, 25,900 feet. 
Cross-section, rectangular with arched roof. Will be driven from 
a center heading 14 feet wide and 8 feet high and from an auxil- 
iary heading 30-50 feet to one side of the main heading, 8 feet 
wide and 7 feet high. Rock, shale and quartzite. Power, steam. 



52 MODERN TUNNELING 

Ventilation, pressure blower. Three Ingersoll-Leyner drills per 
heading. Horizontal bar mounting. Three shifts per day. 
Three drillers, two helpers, and four to six muckers per shift. 
Mule haulage. Work on portal excavation started August, 1913. 
Reference, private communication to the authors. 

Second Raton Hill tunnel: Raton Pass, Colorado. Purpose, 
railway. Length, 2,790 feet. Cross-section, horseshoe, 22 feet 
wide and 29 feet high. Rock, shale, sandstone, and a 3-foot bed 
of soft coal. Reference, Engineering Record, April 4, 1908, page 
461. 

^^SpiraV^ tunnels: Selkirk Mountain, British Columbia. Pur- 
pose, railway. Length, No. i, 3,200 feet; No. 2, 2,890 feet. 
Cross-section, arched roof, 22 feet wide, 27 feet high. Rock, 
limestone. Power, steam. Six and eight Ingersoll-Rand drills 
in the heading. Mounting, vertical column. Two shifts per day. 
Six and eight drillers, six and eight helpers per shift. A Marion 
shovel operated by compressed air used for mucking. Horse 
haulage, 108-cubic-foot cars. All timbered. Average monthly 
progress per heading, 105 feet. Started, January, 1908; com- 
pleted, June, 1909. References, Engineering News, November 10, 
1 9 10, page 512; Compressed Air Magazine, February, 191 1, page 
5.931- 



I 



CHAPTER IV 

CHOICE OF POWER FOR TUNNEL WORK 

SOURCES OF POWER 

While the power for tunnel operations may be obtained from 
various sources, in general practice at present it is produced 
primarily from either steam or flowing water. Although, as far 
as could be ascertained, the gas-producer used in connection with 
internal-combustion engines has been installed at but one tunnel, 
nevertheless it offers a third possibihty as a source of power 
which will have to be considered more and more seriously in the 
design of future plants. It is true that in the early stages of its 
development, when the principles governing its design, construc- 
tion, and operation were not well understood, the gas-producer 
was not rehable and acquired a bad reputation among tunnel 
men, a situation augmented perhaps by the extravagant claims 
of manufacturers or the overzealousness of salesmen. But within 
the last few years, as its principles have become better known 
through study and experiment, the gas-producer has developed 
rapidly — so rapidly, in fact, that few people realize that it is 
to-day as reliable and rugged a piece of apparatus as an ordinary 
boiler, or that its consumption of fuel is only one-third as great, 
or that the labor to operate it need not be one whit more skilled. 
It is true that gasoHne engines are occasionally used to furnish 
power in tunnel operations, but they have been confined either to 
temporary plants or to small and isolated units of machinery. 
In localities where petroleum is cheap, it is probable that an oil 
engine of the Diesel type, with its wonderful fuel economy, 
may be found the cheapest means of producing power. Elec- 
tricity, especially where it is used at tunnel plants to operate 
prime moving machinery, is sometimes considered a source of 
power; but since the current so employed has to be generated 
elsewhere, usually from steam or water, but possibly from pro- 

53 



54 



MODERN TUNNELING 



ducer gas, petroleum, or gasoline, electricity is merely a conve- 
nient form for transmitting power instead of a source. 



PRODUCTION OF POWER 

Water-power. — In tunneling the machines most frequently 
employed for the utilization of water-power are of the impulse 
type, similar to the Pel ton wheel, illustrated in Figure 8. Such 







Fig. 8. Standard Pelton wheel. 

a wheel is driven by the force of a stream of water issuing from 
a nozle, acting against vanes or buckets on the circumference 
of the wheel, and is well adapted for use with a relatively small 
volume of water under high head. The efficiency of the machine 
is dependent upvon the way the vanes or buckets reverse the direc- 
tion of the water discharged upon them; hence they usually 
conform to a curve which is very carefully designed to avoid 
loss of power through eddies and friction as the water strikes the 
vane. There may be more than one nozle in order to obtain 
greater power, or, if high rotative speed is desired, a small wheel 



CHOICE OF POWER FOR TUNNEL WORK 55 

with multiple nozles may be substituted for a large one. In 
order to obtain the best results, the peripheral speed of the cups 
or vanes should be between 42 and 48 per cent of the speed of 
the water issuing from the nozle. Impulse wheels are manufac- 
tured in many different designs, sizes, and speeds, adapted for 
working imder widely diverse conditions. Those observed at 
the different tunnels examined were, as far as could be learned, 
giving very satisfactory service. 

The turbine wheel, in which the force of the water is made to 
act through suitable guides upon all the vanes or blades simul- 
taneously, affords another means of utiHzing water-power and 
may be designed for either high or low heads. Its use is limited, 
however, especially with high heads, to localities where clear 
water is available (as, for example, at Niagara Falls) because of 
the destructive abrasive action of sand and grit upon the guides. 
With low heads this action is not so marked. Since the source 
of water-power in the vicinity of tunnels and adits is in most 
cases to be found in streams furnishing high heads and which at 
certain seasons of the year carry large amounts of sediment, the 
use of turbine wheels for such plants is prohibitive unless large 
setthng basins can be provided. 

The hydraulic compressor, converting the energy of water 
directly into compressed air, offers a third method for utiHzing 
water-power. The earliest type operates upon the principle of 
the hydraulic ram, in which a column of water is allowed to ac- 
quire velocity and is then suddenly checked, developing intermit- 
tently for a short space of time pressure much greater than that 
due to the head of the column of water. This pressure is em- 
ployed in compressing air. Sommeiller in about i860 designed a 
machine of this type for use at the Mt. Cenis tunnel. Such 
compressors require rather high heads and have low efficiency. 
Although conditions might be such as to make the use of com- 
pressors of this type desirable, the water-power they require can 
generally be utilized more advantageously in some other manner. 

The hydraulic compressor recently developed by C. H. Taylor, 
introducing air into a column of water and compressing it as they 
fall together to the bottom of a shaft where the air is separated 



56 



MODERN TUNNELING 



and collected, is very efficient and requires only a small amount 
of attention, although the cost of construction prohibits its use 
except for installations much larger than those ordinarily re- 
quired for tunnel work. The latest installation of this system, 
which was completed in June, 1910, is situated at Ragged Chutes, 




Fig. 9. Diagrammatic section through Taylor hydraulic compressor at 

Cobalt. 

on the Montreal River, and suppHes air to the mining district 
near Cobalt, Ontario. 

At this plant, a concrete dam diverts water from the river, 
above the rapids, to the tops of two circular shafts 8^^ feet in 
diameter, where, by means of suitable apparatus, a large quan- 
tity of air is introduced into the water in the form of bubbles. 
The mixed water and air descend the shafts (350 feet in depth) 
and start through a passage 1,000 feet long. The passage as 
shown in Figure 9 is so designed that the compressed air is 
permitted to rise to the surface of the water and is collected, 



CHOICE OF POWER FOR TUNNEL WORK 57 

partly along the top of the passage and partly in a large collecting 
chamber which has been excavated near the end of the passage. 
The waste water then rises 298 feet through a shaft 22 feet in 
diameter and is discharged into the river below the rapids. 
The air is drawn from the top of the chamber at a pressure of 
120 pounds to the square inch and is transmitted by a 20-inch 
main to the mines nine miles distant. The capacity of the 
plant is the compression of 40,000 cubic feet of free air per 
minute to 120 pounds per square inch. 

The famiHar overshot, breast, and undershot wheels are not 
used to drive machinery for tunnel work, because of their large 
size for the amount of power developed, as well as the trouble of 
their maintenance. The overshot wheel utilizes the weight of 
the water, chiefly, and is best suited for low heads. Its efficiency 
is greatest when enough water is supphed to fill the buckets 
completely. The breast wheel utihzes both the weight and the 
velocity of the water, and its efficiency is less, though it can be 
used with even lower heads of water than the overshot wheel. 
The undershot wheel uses only the velocity of the water, and has 
the least efficiency of the three types, but it requires practically 
no head. Its efficiency is at a maximum when the water is con- 
fined laterally. 

The following table, which is based upon actual results, 
shows the efficiency of different t>^es of water motors: 

PERCENTAGE OF THEORETICAL HORSE-POWER REALIZED 
BY X'ARIOrS WATER :\IOTORS 

Impulse wheels 7o~85% 

Turbine wheels 75~S5 

Overshot wheels 60-65 

Breast wheels 50-60 

Undershot wheels 30~5o 

Results obtained at the testing flume of the Holyoke (Mass.) 
Water Company, whose tests are taken as standard by American 
engineers, show efficiencies for turbine wheels under favorable 
conditions of over 90 per cent,* but this is unusual, the figures 

* Trans. A. S. C. E., Vol. XLIV (1910), p. 2>22. 



58 MODERN TUNNELING 

above being much nearer ordinary practice. The efficiency of 
hydraulic compressors of the ram type is about 30 to 40 per cent, 
while the Taylor compressor at Cobalt is said to utilize at least 
75 per cent of the theoretical power of the water. 

Steam. — Steam engines are of two types, reciprocating and 
turbine. In the reciprocating engine, power is developed by the 
pressure and expansion of steam in a cylinder acting against a 
moving piston. Such engines may be either simple or compound, 
both forms being used in tunnel plants. In the former, the 
total expansion of the steam and consequent reduction of press- 
ure take place in one cylinder, while in the latter only a portion 
of the expansion takes place in the first cynnder, and the steam, 
under somewhat reduced pressure, is expanded further in a 
second cyHnder, necessarily larger because of the lower pressure 
of the steam. 

The steam turbine is similar in principle to the water-wheel, 
except that steam instead of water is the motive fluid. Owing 
to their economy, small size per unit of power, and freedom 
from vibration, their use is steadily increasing on both 
land and sea. Modern steam turbines in sizes of 250 to 
500 horse-power, with a steam pressure of 150 pounds and 
a 28-inch vacuum, will develop a kilowatt-hour with a con- 
sumption of from 18 to 20 pounds of steam. A recently published 
series of shop tests on a 300-kilowatt Swiss condensing turbine 
showed that with ii2j^ pounds of steam and a 96.6 per 
cent, vacuum it was able to produce a kilowatt-hour with 16. i 
pounds of steam. The difficulty of reducing the high rotative 
speed of the turbine engine down to the restricted speed of 
reciprocating machinery has prevented, until recently, the use of 
turbine engines in tunnel installations; but, with the advent 
of the turbo-compressor, we may expect to see them dividing 
the field, or, perhaps, entirely displacing the cumbersome 
reciprocating plants now in vogue. 

Internal Combustion. — Internal-combustion engines devel- 
op power from the pressure produced by the explosion or rapid 
combustion (confined in a suitable cylinder) of a mixture con- 
taining the proper proportions of air and a gasified fuel. The 



CHOICE OF POWER FOR TUNNEL WORK 59 

source of the fuel gas may be gasoline, kerosene distillate, or 
even crude petroleum, or it may be generated from coal by dis- 
tillation in a retort, or by a gas-producer, and the engines are 
usually designated by the kind of fuel for which they are adapted, 
as, for example, oil engines, gasoline engines, or producer-gas 
engines. As far as could be ascertained these latter two are 
the only types now used in tunneling. 

Although the gasoline engine has been developed with 
wonderful rapidity during the last twenty-five years in con- 
nection with the automobile industry, the use of engines of 
this t}pe for tunnel work has been confined to a very limited 
field, viz., the operation of isolated or not easily accessible 
machinery. As prime movers for tunnel plants of any magni- 
tude they cannot compete, under most circumstances, with 
machines using other forms of power, and, on this account, their 
appHcation has been confined either to enterprises small in 
scope or to the temporary and early development stage of larger 
projects, where they are sometimes installed to begin the work 
at locations by nature inaccessible for non-portable units of 
heavier machinery, pending the construction of a special road- 
way or a transmission fine. ^lost manufacturers of air com- 
pressors have recently begun to supply air compressors directly 
driven by internal combustion engines, although as yet only the 
smaller sizes of gasoline engines are being used. With suitable 
adaptations, the principle might be appKed equally well to the 
larger sizes using oil or gas as fuel. Within the last two years 
gasoHne engines have been successfully employed in locomotives 
for haulage in coal mines, and there are now over one hundred of 
them in operation. These machines are equally suitable for 
tunneling operations, and will, no doubt, be used extensively 
for this purpose in the near future. 

The only use of producer-gas engines in tunnel work to date, 
as far as could be learned, was at the power plant for the tunnel 
under the Thames River recently completed connecting North 
and South Woolwich. Since the tunnel was constructed under 
compressed-air pressure, absolute rehabihty in the power plant 
was required to avoid a stoppage of pressure which might 



60 MODERN TUNNELING 

possibly result in serious damage to the tunnel. At this plant, 
as described in The Engineer,^ three engines, each of 150 b. h. p. 
when running at 180 revolutions per minute, were supplied 
with gas from suction producers using Scotch anthracite coal, 
and were connected to a central shaft which transmitted power 
to four air compressors and four dynamos. The plant was 
operated continuously from July, 1910, until the end of Decem- 
ber, 191 1, except during October and November, 1910, when 
after the vertical shaft had been completed the plant was pur- 
posely stopped while making preparations to start tunneling. 
Although it is not within the province of this report to 
discuss the gas-producer in any detail, the following brief descrip- 
tion is quoted from Bureau of Mines Bulletin 16: 

"The simplest form of gas-producer for power-gas generation is a 
vertical cylinder of iron or masonry, lined with fire-brick, having a 
grate near the bottom, an opening in the top for charging fuel, a 
smaller opening near the top for the outlet of the gas, and one near the 
bottom for the admission of air. Openings are also provided at 
various heights on the sides, through which the interior may be 
reached for poking the fuel bed, inspecting and cleaning the interior, 
making repairs, and removing ashes. To prevent the entrance of air 
except through the proper openings, which are covered by gas-tight 
doors, the charging opening is generally a small chamber, guarded by 
gas-tight doors at the bottom and top, which prevents the escape 
of the gas and the ingress of air while the producer is being 
recharged. 

Simple gas-producers such as described above furnish uncleansed 
gas, which contains so much dust and other foreign matter that it is 
unsatisfactory for use, especially in gas engines. Power-gas pro- 
ducers are therefore provided with apparatus for cleansing the gas, 
known as scrubbers, through which the gas passes after leaving the 
producer. The scrubber in its simplest form is a cylindrical chamber 
filled with some porous material like coke or shavings, which is kept 
constantly wet. The gas, in passing through this wet material, 
leaves behind most of the soUd and liquid impurities it contains. 

In addition to the scrubber, many gas-producers have attach- 
ments for preheating the air admitted for combustion, so that it 
enters the fire at a temperature sufficiently high to prevent cooling 

* The Engineer, London, January 12, 1912, p. 46: "Temporary Power 
Plant for Woolwich Footway Tunnel," two pages illustrated. 



CHOICE OF POWER FOR TUNNEL WORK 61 

of the fuel. Such attachments make use of the heat of the off-going 
gases, and are called regenerators. 

The form of producer in most general use for generating gas 
for the development of power, especially in gas engines, is that supply- 
ing gas directly to the engine, which draws the air and steam through 
the fuel bed by means of the suction stroke of the piston. The 
suction-producer, as it is termed, has been largely restricted to the use 
of anthracite, coke, charcoal, and other fuels containing a low per- 
centage of tarry compounds. When bituminous fuels are used these 
tarry compounds are likely to be carried over with the fixed gases 
into the engine and, condensing there, clog the valves, pipes, and other 
working parts, despite scrubbing apparatus. Recent improvements 
in methods of scrubbing, however, have so modified the older practice 
as to make the use of fuels rich in volatiles comparatively free from 
such accidents, and their use in the suction type of producer is in- 
creasing. 

The pressure gas-producer is so designed that the air and steam 
necessary to develop the gas are forced into the fuel bed under enough 
pressure to drive the gases generated through the fuel bed and scrub- 
bing apparatus into a gas holder. The gas is thus generated indepen- 
dently of the piston stroke of the engine, and may be thoroughly 
cleansed of tars and ash before it is used. For this reason the pressure 
type of gas-producer is well titted for using bituminous coal, lignite, and 
peat. The down-draught or inverted -draught gas-producer, in which 
the heavier products of distillation are all decomposed and changed 
into simple permanent gases, constitutes a third t^'pe. In power-gas 
producers of this type the heated gases, rich in vaporized hydrocarbons, 
tars, and hea\y gases, are drawn by exhaust fans from the top of the 
producer, where they accumulate above the freshly added fuel, down 
through the fuel bed. In the fuel bed, by contact with the heated 
carbon, they are converted into carbon monoxide and hydrogen, which, 
after cleansing, can be either stored in receivers or used in engines." 

The essential principles in the process of making gas in a 
producer may be outlined very briefly as follows : In comparison 
with steam-boiler practice, the fuel bed is very deep and con- 
tains three zones — combustion, incandescence, and distillation. 
A portion of the coal is burned in the combustion zone, where a 
limited amount of air is suppKed for this purpose, and the 
resulting gases are passed through the remainder of the fuel 
bed. In the incandescent zone the hot gases combine chemically 
with some of the constituents of the glowing coal (unburnt 



62 MODERN TUNNELING 

as yet, because of lack of air) and form new gases which have a 
fuel value. These, together with the gases driven off from the 
fresh coal by heat in the distillation zone, supply the fuel portion 
of the mixture exploded in the engine. Steam is also employed 
in most types of gas-producers because its introduction with the 
air for combustion assists in the formation of gases of the right 
composition. 

For a more detailed discussion of this subject the reader 
is referred to the bibliography accompanying this volume. 

Although, as far as could be learned, oil engines of the Diesel 
type have not yet been employed in tunnel power plants, their 
marked success in other fields more than -warrants the dis- 
cussion of the possibility of their use in tunnel work. The 
essential feature which differentiates the Diesel machine from 
other internal-combustion engines is the fact that instead of draw- 
ing into the cylinder an explosive mixture containing a com- 
bustible gas (such as producer-gas, gasoline vapor, kerosene, or 
even crude petroleum previously volatilized by heat), and then 
compressing this mixture and exploding it by means of an 
electric spark or some other suitable device, the Diesel engine 
compresses air alone, and when it is under its highest pressure 
(approximately 300 pounds per square inch, which is much 
greater than that usually attained in other types of internal 
combustion engines) injects into the cylinder a spray of finely 
atomized oil. During the compression of the air to the required 
pressure it will have reached a temperature of more than 1000° F., 
more than safhcient to ignite the oil instantly without the use 
of an electric spark, hot plate, or other similar device. 

The chief advantage of the Diesel engine is economy of fuel. 
It is a well-known fact that the rapidity and completeness of 
any combustion are greatly increased by pressure; it is not 
surprising, therefore, that under the higher pressures which 
prevail in this machine better results can be obtained from a 
smaller amount of oil. The extremely fine atomization of the 
fuel due to the jet of compressed air (under a pressure of 300 
to 500 pounds per square inch higher than that in the cylinder) 
by which the oil is injected is undoubtedly another great con- 



CHOICE OF POWER FOR TUNNEL WORK 63 

tributing factor. And again, since the scavenging of the exhaust 
gases from the previous explosion is effected by air only, instead 
of a mixture of air and fuel, as is the case in other types of internal- 
combustion engines, there is no possibility of loss of fuel through 
the exhaust valves during this process, a saving which is ex- 
tremely important where the engines are designed for a two- 
stroke cycle. 

In addition to the advantage of fuel economy, however, 
the Diesel engine does not require frequent cleaning, as is the 
case with oil engines depending upon a hot plate or a similar 
device for the ignition of the explosive mixture. It also dis- 
penses with the carbureter, so necessary for the gasoline engine, 
and which is always a source of more or less trouble and annoy- 
ance. And, in addition, since the mixture being compressed in 
the cylinder of a Diesel engine is not an explosive one, allowance 
does not have to be made in the design of the cylinder and other 
parts for undue stresses and strains which might result from a 
premature ignition of the charge, caused, perhaps, by a glowing 
piece of carbon on the cylinder wall or by a heated piston, 
an occurrence which is not infrequent in other engines, as any 
automobilist will testify. Although some provision can, of 
course, be made for these shocks, their force and violence cannot 
always be correctly foreseen or sufficient allowance made for 
them, and there have been many instances of disastrous results 
arising from premature ignitions in internal-combustion engines 
of the usual types. 

The principal disadvantage of the Diesel engine, on the other 
hand, is that of high first cost, and this would prohibit its use for 
tunnel work of short duration. The price of this machine has 
recently been greatly reduced abroad, however, and it is certain 
to be reduced in America, now that manufacturers in this 
country are equipped with suitable apparatus and prepared to 
execute the high class of workmanship required in its con- 
struction, so that in the near future this drawback may dis- 
appear. But even now, if the time required for the completion 
of the work is to be long enough, or the amount of power to be 
used is great enough to warrant a heavy initial outlay in order 



64 MODERN TUNNELING 

to effect a saving in operating cost, the choice of a Diesel engine 
should be seriously considered. 

Electric Motors. — Electric motors may be designed either 
for direct or alternating current. Where used as prime movers 
at the tunnel plants visited they were of the second type only 
and operated at comparatively low voltages, 440 volts being the 
usual figure. Their power was generally transmitted to the 
remainder of the machinery by means of belts, but at one or 
two places on the New York Aqueduct, ''direct-connected" 
electric-driven air compressors were noticed. 

TRANSMISSION OF POWER 

Electricity, because of its economy and its freedom from 
limiting distances, is the favored means for transmitting to a 
tunnel the power generated at some remote station. It pos- 
sesses one well-known disadvantage, that of occasional inter- 
ruption, especially where distances are great and tension high, 
because of unavoidable hindrance to service due to electrical 
storms or other atmospheric agencies. On the other hand, 
producer-gas transmission has possibilities which deserve to be 
considered seriously in this connection. This form of conveying 
power has been recently taken up from the realm of mere con- 
jecture and demonstrated as a practical system, both in this 
country, at Pittsburgh where natural gas is piped over distances 
as great as 200 miles, and in England, where producer gas is 
supplied to points within a radius of 160 miles, with trans- 
mission losses even less than when electricity is used. In its 
apphcation to tunnel operations, producer gas can be generated 
in a plant conveniently situated on a railroad siding or some 
other readily accessible place, and the power piped to internal- 
combustion engines at the tunnel portal. 

Where distances are comparatively short (that is, less than 
five miles or so) electricity is rivaled by compressed air, and 
the competition grows more keen as the length of the trans- 
mission system decreases. This is possible because where 
pneumatic drills are employed, compressed air, in spite of its 



CHOICE OF POWER FOR TUNNEL WORK 65 

low efficiency and high cost, is necessary for their operation; 
and even were electric transmission chosen, the power would 
need to be converted ultimately into compressed air at the 
tunnel. Hence it is the usual practice to produce the compressed 
air at once, thus avoiding the extra machinery and the additional 
operating losses of electric transmission. 

CHOICE OF POWER 

A number of factors enter into the choice of power for tun- 
nehng operations. To begin with, the plant is usually short 
lived. Then, too, the influence of such local conditions as 
accessibility, distance from a railroad, the availability of water- 
power, etc., is strongly felt. Each method of deriving power 
has also certain peculiarities which render it particularly adapt- 
able to different conditions. Among these may be mentioned 
the cost of installation, of labor, of fuel, of interest and deprecia- 
tion, and other operating expenses. Aside from all this, it is 
often necessary to decide between the production of power at 
the plant or elsewhere and the purchase of power from an 
established hydro-electric company. Some of these factors we 
shall discuss briefly. 

Duration of Plant. — At many tunnel power plants, in di- 
rect contrast with those used in manufacturing, the equipment is 
required only for the comparatively short time of actual tunnel 
construction. Thus it becomes a delicate problem to determine 
just how far one is justified in the purchase of machinery and 
apparatus for utilizing all the various economies that may be 
effected in the production of power. It is difficult to decide 
whether it would not be better in the end to install less costly 
machinery that would necessitate sKghtly higher expense in 
operating and maintaining than to tie up extra capital in 
equipment that would be of no further use when the tunnel is 
completed. Of course, the shorter the probable Kfe of the 
plant the more would one be justified in such a course ; although, 
if the equipment can be transferred upon the completion of the 
tunnel to other projects, this would so prolong its period of 



i66 MODERN TUNNELING 

usefulness that the original expenditure of capital could properly 
and with true economy be greater. A notable instance of this 
was observed on the Los Angeles Aqueduct, where as far as 
possible, upon the completion of one of the numerous tunnels, 
the equipment was transferred and used in power plants at other 
tunnels whose construction had not yet been begun. If a central 
station is being considered, where a large amount of power is 
to be generated, the purchase of apparatus from the main view- 
point of economy in operation is again the far-sighted policy. 
This was the case at the Rondout Siphon Tunnel, but at the 
average mining tunnel or adit the converse is more often likely 
to be true. 

Accessibility. — Tunnels are often located at places very 
difficult of access. They may be so situated as to make the 
installation of heavy machinery no easy matter, as, for example, 
where the road from the nearest railroad is poor and the grade 
very steep; or they may be at a great distance from the nearest 
siding, so that if a form of power be chosen that requires coal, 
the delivery of this fuel is not only very costly, but also most 
uncertain and difhcult in some seasons of the year. Such 
conditions are favorable for the adoption of power transmission 
in some form from a waterfall or rapid, if one be located near 
enough, or, lacking these natural advantages, from a fuel plant 
installed at some point more readily accessible. 

Cost of Installation. — The cost of installing water-wheels 
is entirely dependent upon local conditions, which are never twice 
alike. Where high heads are available and the quantity of 
water required is not large, it can be conveyed to the water- 
wheel by small flumes or pipes which are comparatively inex- 
pensive. For example, at the Carter tunnel (see Figure lo), with 
an available head of 145 feet, a flume 16 by 48 inches inside 
and 5,000 feet in length is sufficient to supply the 200 horse- 
power developed. At the Laramie-Poudre tunnel, with a 
static head of 268 feet, 400 horse-power was conveyed to the 
tunnel plant by a wooden-stave 22-inch pipe line, 8,500 feet in 
length. The Utah Metals tunnel secures water from two 
sources: the first has a 700-foot head, using 2,500 feet of 12-inch, 



CHOICE OF POWER FOR TUNNEL WORK 



67 



1,900 feet of lo-inch, and 100 feet of 8-inch spiral steel riveted 
pipe, furnishing 170 horse-power; the second, with 750 foot 
head, employs 2,000 feet of 12-inch, 1,000 feet of 8-inch, 3,000 
feet of 6-inch pipe in producing 55 horse-power. Where heads 
are low, however, retaining dams are usually necessary. At 




Fig. 10. View showing end of flume, mill, dump, and other surface features 
at Carter tunnel. 



best these are a costly expedient and their expense increases 
enormously with their height. With low heads, larger flumes 
are also required to convey the greater quantity of water. 
At the Nisqually tunnel, illustrated in Figure 11, a low dam and 
a wooden flume 6 by 8 feet in cross-section and 1,200 feet long 
were used. The water was delivered to a turbine wheel under 
an effective head of 29 feet which generates 1,000 horse-power. 
One has only to consider some of the very expensive dams on the 




cr 

w 

IB 

B 

3 



CHOICE OF POWER FOR TUNNEL WORK 69 

larger rivers, furnishing power for manufacturing purposes, in 
order to realize how great the cost of installation may be where 
low heads only are utilized. It is fortunately true, however, 
that where water-power is obtainable for tunnel work high 
heads are usually available also, and the less expensive flumes 
or pipe lines of moderate length can be utilized. 

The cost of the machinery actually within a tunnel power- 
house is greater for steam than for water-power or electricity; 
but if, as should be done to make the figures truly comparable, 
the cost of the dam and flume (or of the transmission line for 
electricity) be taken into consideration, the advantage. is usually 
reversed. It is somewhat cheaper to install a steam plant than 
one using producer gas and having engines of the same capacity, 
but the dift'erence is not great. R. H. Fernald,* after a study 
of many tables of costs, applying to other uses, however, than 
tunnel work, concludes that ''complete producer-gas installa- 
tions for the larger plants, say from 4,000 to 5,000 horse-power, 
cost about the same as those of first-class steam plants of the 
same rating. With smaller installations the balance is prob- 
ably in favor of the steam plant." Since it is not customary 
in tunnel work to install machinery designed to effect all the 
refinements of steam economy found in permanent plants, it is 
probable that the first cost of the average steam plant for tunnel 
work is less than those upon which Mr. Fernald's estimates 
are based, in which case the comparison would be even more 
favorable to steam. This is partly offset by the fact that the 
price of gas-producers and engines is constantly being lowered, 
and by the fact that the cost of actually placing the machinery 
would be less for the gas-producer — considerably in some cases, 
appreciably in all 

The initial expense of installing any of the various systems 
for transmitting power is dependent upon two factors: (i) the 
cost of the machinery required to produce the power, to convert 
it into the form suitable for transmission, and to reconvert 
it into the form adapted to the machines using it; and (2) the 



* Bull. 9, B. of M., p. 31. 



70 MODERN TUNNELING 

cost of the transmission line. Except for a slight increase in 
capacity, to provide for losses in transmission, the factor of 
machinery cost under any given conditions is independent of 
the distance over which power is to be delivered, but the cost 
of the line, as will become apparent later, increases considerably 
faster than its length, other things being equal. If the power is 
required ultimately for the operation of air drills, practically 
the same size of compressor will be necessary whether electric, 
air, or gas transmission is employed, and the cost of boiler, 
engine, foundations, etc., in the case of electricity or air will 
approximately balance the cost of the producer, engine, founda- 
tions, etc., for gas. Air transmission would require practically 
no other machinery than that just mentioned; but gas, on 
the other hand, would need a blower of some sort to force it 
through the line, while electricity would require, in addition, 
a generator, motor, transformers, extra foundations, etc. A 
list of the three forms of power transmission made, according 
to increasing machinery-cost factor, would be air, gas, and 
electricity. 

The cost of an electric-transmission line may be divided into 
three parts: first, the metallic part of the circuit; second, in- 
sulating the conductor; and, third, erecting or installing the line. 
Although a detailed discussion of this subject is beyond the 
proper scope of this book, it can be shown that, for a stated 
power loss and a given distance, the weight of the metalHc 
conductor required to transmit a definite amount of power is 
inversely proportional to the square of the voltage employed. 
On the other hand, the cost of insulation increases rapidly with 
the potential, and the cost of erection, complicated by steel 
towers, etc., is greatly augmented at high voltages. Thus the 
economical transmission of a given amount of power for a 
stated distance is limited by the maximum voltage which may 
be used without the increased cost of installation and erection 
destroying the saving in the cost of copper. 

Any attempt to go into the complicated processes necessary 
to ascertain the most advantageous voltage for a long distance- 
transmission Kne would be out of place here; but, for the short 



CHOICE OF POWER FOR TUNNEL WORK 71 

distances and small amounts of power commonly employed in 
tunneling operations, the following rule of thumb will suffice 
to give a close approximation to the most carefully made calcula- 
tions. Multiply the distance to be traversed in miles by i,ooo 
and select the voltage of the nearest commercial size of trans- 
former to this figure. The standard voltages of transformers 
now in use are 220, 440, 660, 1,100, 2,200, 6,600, 11,000, 
22,000, 33,000, 66,000. For instance, if the distance from the 
power station to the tunnel plant is five miles, select a voltage of 
6,600; if the distance is ten miles, a voltage of 1 1 ,000. Where the 
distance falls midway between transformer steps, use the voltage 
which will find most ready sale for the apparatus when the work 
is completed. 

Since there are certain difficulties in the construction of 
direct-current generators for voltages higher than 600, alternat- 
ing current is generally employed for transmission lines. This 
form also possesses a very important additional advantage in 
the ease with which it may be changed from low to high potential, 
and vice versa. When high tension is employed in transmission 
of electrical power, the voltage at the generating station is 
usually comparatively low, and is "stepped up" by transformers 
to the desired potential for the fine and is reduced again by 
transformers at the tunnel plant. 

The following figures, which show the installation cost of an 
electric-transmission line for different voltages and distances, 
assuming approximately 10 per cent drop in the line, are based 
upon data kindly furnished by the General Electric Co.^ 



* 



I. 200 H.P. — I mile — 440 v., direct current. 

Poles, cross-arms, insulators, and fittings (poles spaced 

100 feet) $375 

33,000 lbs. copper cable, 500,000 C. M. (four conductors 

required), at 18X cents lb 6,025 

Cost of erection 300 

Total $6,700 



* Freight, right of way, surveying, and engineering are not included in 
these data. 



72 MODERN TUNNELING 

2. 200 H.P. — I mile — 440 v., 3-phase, 60-cycle, alternating 

current. 
Poles, cross-arms, insulators, and fittings (poles spaced 

100 feet) $415 

34,000 lbs. copper cable, 350,000 CM. (six conductors 

required) at 17^ cents 6,035 

Cost of erection 375 



Total $6,825 

3. 200 H.P. — I mile — 1,100 v., 3-phase, 60-cycle, alternating 

current. 
Poles, cross-arms, insulators, and fittings (poles spaced 

125 feet) $385 

5,100 lbs. copper cable, B. & S. No. o (three conductors 

required) at 17^ cents 905 

Cost of erection 265 

Six transformers, 1,100: 440 volts, with switches, etc., 

erected 2,900 



Total $4,455 

4. 200 H.P. — 5 miles — 1,100 v., 3-phase, 60-cycle, alternating 

current. 
Poles, cross-arms, insulators, and fittings (poles spaced 

125 feet) $1,870 

122,000 lbs. copper wire, B. & S. No. 000 (nine conductors 

required) at 17^ cents 21,650 

Cost of erection 1,580 

Six transformers, 1,100: 440 v., with switches, etc., erected 2,900 

Total $28,000 

5. 200 H.P. — 5 miles — 6,600 v., 3-phase, 60-cycle, alternating 

current. 
Poles, cross-arms, insulators, and fittings (poles spaced 

125 feet) $1,870 

6,500 lbs. copper wire, B. & S. No. 6 (three conductors 

required) at 17^ cents 1,150 

Cost of erection i ,080 

Six transformers, 6,600: 440 v., with switches, etc., erected 3,700 

Total $7,800 



I 



CHOICE OF POWER FOR TUNNEL WORK 73 

6. 200 H.P. — 25 miles — 6,600 v., 3-phase, 60 cycle, alter- 

nating current. 
Poles, cross arms, insulators, and fittings (poles spaced 

125 feet) $9;35o 

103,000 lbs. copper wire, B. & S. No. i (three conductors 

required) at 17^ cents 18,300 

Cost of erection 5jI5o 

Six transformers, 6,600: 440 v. with switches, etc., erected 3,700 

Total $36,500 

7. 200 H.P. — 25 miles — 22,000 v., 3-phase, 60 cycle, alter- 

nating current. 
Poles, cross arms, insulators, and fittings (poles spaced 

125 feet) $9,900 

33,000 lbs. copper wire, B. & S., No. 6 (three conductors 

required) at 17^ cents 5, 860 

Cost of erection 5,190 

Six transformers, 22,000: 440 v., with switches, etc., erected 5,200 

Total $26,150 

The Pneumo-Electric Machine Co.* have estimated that if 
compressed air were used to transmit 200 horse-power one mile, 
allowing 10 per cent, loss at 80 pounds pressure, an 8-inch pipe 
would be required which, at $1.78 per foot, would cost $8,400. 
Calculations show that in order to transmit the same amount of 
power in the form of producer-gas containing 120 B. t. u. per 
cubic foot, the required pipe would need to be only 4 inches in 
diameter, costing, at 70 cents per foot, approximately $3,700. 
To both these values should be added the expense of la>ing the 
line, but this figure would be relatively small compared to the 
cost of the pipe. 

Where the power is ultimately required for use in air drills 
and is to be transmitted only for short distances, compressed 
air is' the cheapest of the three methods as regards installation 
cost, the higher machinery factor required by the other systems 
more than balancing the expensive air pipe-line. The field for 
producer-gas transmission (with its machinery factor slightly 

* Mining and Scientific Press, May 14, 1910, p. 700, 



74 MODERN TUNNELING 

greater than air yet less than electricity, and its line factor just 
the reverse) lies in the medium distances — beyond the economical 
raiige for air, but still too short to warrant the cost of the extra 
electrical machinery. For long distances, on the other hand, 
electric transmission at high tension is, of course, preeminent. 

Labor. — Tunnel power plants are generally not large enough 
to occupy the entire time of even one operator, hence it is impos- 
sible to prevent their being over-m^anned. The amount of labor 
required does not as a rule, therefore, seriously affect the choice 
of power. At a tunnel plant using water-wheels, hydraulic air 
compressors, or electric motors as prime movers, one man per 
shift is sufficient. Even then, as was the case at the Laramie- 
Poudre tunnel, it is not unusual to make these 12 -hour shifts, 
thus requiring but two men per day; or, as at the Carter 
tunnel, for a portion of his time the engineer is employed at other 
work. If the results obtained from practice in other Hues be 
accepted, a producer-gas plant would require no more exacting 
attention, it being not unusual for one man per shift to operate 
plants which develop as high as 750 or 1,000 horse-power. A 
similar steam plant, on the other hand, would require at least 
two firemen in addition to the engineer. In larger steam installa- 
tions the amount of labor required is naturally not so great in 
proportion to the horse-power produced. For example, at the 
Rondout Siphon 8 men per 8-hour shift were able to operate 
a steam plant rated at 4,000 horse-power and containing 10 air 
compressors of 2,400 cubic feet capacity each. 

Fuel Consumption. — If the charge for delivering it be in- 
cluded in the price, at most tunnel plants the cost of fuel is high, 
hence the amount of it required is of great importance. Steam 
plants require much more coal than gas plants of the same size ; 
for although in large installations, with every means for eff'ecting 
thermal economies, steam plants may be operated with as Httle as 
two pounds of high-grade fuel per brake horse-power hour, in 
small plants such as are used in tunnel work a fuel consumption 
as low as three pounds would be exceptional, and four or five 
pounds is more likely to be required. With producer-gas, on the 
other hand, it has been repeatedly demonstrated that internal 



CHOICE OF POWER FOR TUNNEL WORK 75 

combustion engines can be operated on less than one pound of coal 
per brake horse-power hour, and at the best plants this figure 
runs as low as three-fourths of a pound. The consumption at the 
Woolwich tunnel plant during a test was .727 pound of Polmaise 
Scotch anthracite per brake horse-power hour. The small inter- 
nal combustion engine has also the additional noteworthy char- 
acteristic of being decidedly efficient in small sizes. The gas 
engine of 50-60 brake horse-power has but a very Httle greater 
fuel consumption per horse-power than the large engines of 500 
or 1,000 brake horse-power. The adoption of a producer-gas 
plant also makes possible the utilization of the fine sizes of an- 
thracite coal such as Nos. 1,2, and 3 buckwheat, which were for- 
merly considered waste, but which are now being screened 
and saved and may be procured at much less cost than the coal 
used in most steam boilers. 

Thermal Efficlency. — The comparatively high fuel con- 
sumption of the steam-engine is due to its low thermal efficiency. 
Although large and economically operated steam plants may real- 
ize perhaps as high as 12 to 15 per cent, of the theoretical energy 
contained in the coal, 5 per cent, is much nearer the value gener- 
ally obtained in ordinary tunnel work. The following table shows 
the distribution of the average heat losses for one year at a well- 
conducted steam plant where the thermal efficiency at the fly- 
wheel was 10 per cent. : 

LOSS OF THEORETICAL HEAT ENERGY AT A 
STEAM PLANT 

Losses due to imperfect combustion, heat absorbed in 
ashes, moisture, etc., heat in flue gases, radiation, etc. 25% 

Loss due to latent heat in exhaust steam 60 

Loss in steam pipes and auxiliaries 3 

Loss due to friction in steam-engines 2 

90% 

The producer-gas engine, on the other hand, operates with a 
much higher thermal efficiency, 20 to 30 per cent, being not un- 
usual in actual practice. Recent exhaustive shop tests of a 
number of first-class foreign-built producer-gas engines, ranging 



76 MODERN TUNNELING . 

in power from 70 to 120 horse-power, gave thermal efficiencies 
at full load of from 31.3 per cent, to 34.9 per cent., and a coal 
consumption of from .72 to .623 pounds per brake horse-power 
hour. The following table, introduced for comparison, shows the 
distribution of losses in a producer-gas plant operating with 
similar economy to the steam plant above: 

THERMAL LOSSES IN PRODUCER-GAS PLANT 

Loss in gas-producer 15% 

Loss in water jacket 21 

Loss from radiation and friction 4 

Loss in exhaust gases 35 

75% 

Purchase of Current. — If the line of an estabhshed electric 
power company runs near enough to the tunnel plant, power is 
often purchased in preference to generating it at the tunnel. In 
such cases the price of current usually ranges from i^ to 2 
cents per kilowatt hour. On the Los Angeles aqueduct the power 
used at all the tunnel plants is obtained from a private trans- 
mission line operated by a separate department of the aqueduct 
organization, and a fiat rate of 1.7 cents per kilowatt hour for 
power is charged against each tunnel, which it is estimated is 
sufficient to operate the system and eventually pay for its instal- 
lation. At one of the tunnels in Colorado, a fiat rate of $2.50 
per horse-power month is charged, to which is added 1.3 cents 
per kilowatt hour used. On a 24-hour day basis this is equiv- 
alent to i^ cents per kilowatt hour. At another tunnel in Colo- 
rado, 2 cents per kilowatt hour is the price of current. At a 
third, the power for the compressor costs $5.50 per horse-power 
month, which is equivalent to i cent per kilowatt hour on a 
24-hour day basis, but at the same tunnel 2 cents per kilowatt 
hour is charged for the current used in the motor generator set 
which operates the trolley system, making the average cost for 
the total power used approximately ij^ cents. At one tunnel 
plant using a very large amount of power, the current is said 
to have cost but yi cents per kilowatt hour, an exceptionally 



CHOICE OF POWER FOR TUNNEL WORK 77 

low figure, but in this case other considerations were involved 
which really made the cost of the electricity greater than 
this. 

The following schedule is used by a number of western hydro- 
electric companies who claim that this method of making a charge 
is ''fair and rational." 



Fixed Charge per Month per Horse-Power of 
Maximum Demand 



Energy Charge 



For the first loo Horse-Power. . $3.25 

For the next 400 Horse-Power. . 2.25 

For the next 500 Horse-Power. . 1.75 

For all additional Horse-Power . i .00 



Add for all energy used as 
shown by meter thirteen 
mills per kilowatt hour for 
the first 40,000 kilowatt 
hours used each month, and 
five mills per kilowatt hour 
for all additional energy. 



The maximum demand shall be determined by the company's 
meters, disregarding starting peaks and those due to short 
circuits or accidents to user's apparatus. 

Interest and Depreciation. — The cost for interest per unit 
of power is dependent upon the amount of capital invested, but 
that for depreciation is somewhat more complicated. In the 
case of water-power, a dam or a ditch would have but very little 
salvage value after the completion of the tunnel; something 
further might be realized from a pipe-line or flume and still more 
from the machinery in the power-house, the total loss of capital 
invested being the sum of these separate items. Hence the 
charge for depreciation would depend upon the relation of the 
different factors to the total cost of installation. A similar 
analysis may be made for other means of producing power. Both 
interest and depreciation charges are dependent also upon the 
hourly use of the plant per day, it being evident that if the plant 
were used 24 hours instead of 12 the same total cost for interest 
and practically the same total loss by depreciation would be dis- 
tributed over double the number of horse-power hours, and 
hence be proportionally less. 



78 . MODERN TUNNELING 

CONCLUSIONS 

In choosing the power to be used for tunnel plants, a water- 
fall or rapid, if either is available, should be given primary con- 
sideration. The chief arguments in favor of this source of power 
are as follows: no fuel is required; the cost for attendance and 
repairs is a minimum; it is comparatively reliable, hence 
obviating losses due to interruptions of service. The one factor 
which might prohibit its choice is the possibility of a high cost 
of installation, with resulting large charge for interest and depre- 
ciation per unit of power. This consideration, dependent entirely 
upon local conditions, usually determines the adoption or rejec- 
tion of a possible water-power plant. Again, where water-power 
is not obtainable directly at the tunnel plant, if it can be secured 
from a waterfall in the neighborhood, the essential factors re- 
main the same with the exception that a means of transmitting 
the power, such as air or electricity, must be chosen, and the cost 
of the transmission system be included in the cost of installation. 
Another possible means of obtaining the advantages of water- 
power is to be found in the purchase of current from an estab- 
lished hydro-electric company. Such a concern is in a position 
to utilize a waterfall, too distant to warrant its development for 
a single tunnel project, and by distributing a large amount of 
power among many permanent customers is enabled to sell it 
very cheaply. In such case, to the price of the power should be 
added the cost of attendance at the tunnel plant and the interest 
and depreciation charges on the necessary equipment. Allow- 
ance must be made for interruptions to service in long-distance 
electrical transmission which are neither unusual nor avoidable. 

The choice of machinery for utilizing water-power is also 
largely governed by local conditions. Since high heads, for which 
impulse- wheels are especially adapted, are generally to be found 
where water-power is available for tunnel work, this type of 
machine is properly chosen in most instances. Turbine wheels 
may be used where the water is clear or can be settled in a 
reservoir, but such conditions are not usually to be found at 
tunnel power plants. The hydrauHc compressor, although prac- 



CHOICE OF POWER FOR TUNNEL WORK 79 

tically automatic and entailing but a small operating expense, 
is so costly to install that it is scarcely to be considered except 
for plants much larger than those usually designed for tunnels. 

According to usual practice, a steam plant would be installed 
if water-power were not available and electricity were not 
purchasable. This is difficult to understand unless it be attrib- 
uted to the supposed unreliability of the gas-producer. The 
usual steam plant for tunnel purposes is, as has been shown, 
very inefficient in its utilization of the energy of coal and has 
a fuel consumption rarely less than 4 or 5 pounds per horse- 
power hour. As regards cost of installation, the balance is 
slightly in favor of steam, but not sufficiently so to overcome 
the disadvantage of higher operating cost. 

The producer-gas plant, on the other hand, is several times 
more efficient in its utilization of heat energy, making possible 
the production of a brake horse-power per hour in some instances 
with as Kttle as one pound of coal. With this plant it is also pos- 
sible to utilize cheaper grades of fuel. The manufacturers of air 
compressors have recently adapted their machines for use with 
internal-combustion engines. It would seem, therefore, if a 
plant using fuel were necessary, that the installation of a 
producer-gas plant under most conditions were more desirable 
than a steam plant. 

As a means of transmitting power for any great distance 
the balance is preponderantly in favor of electric transmission 
at high tension. In tunnel work and over comparatively short 
distances, compressed air is able to compete with it because 
the air drills require this form of power for their operation. 
When it is necessary to obtain power from coal there seems to 
be a field for producer-gas transmission in the medium distances, 
where the cost of the line and the power losses in transmission 
prohibit the use of air, but where the cost of the extra electrical 
machinery is still not warranted by the saving in cost of line. 



CHAPTER V 
AIR COMPRESSORS 

Although an air compressor is the machine invariably 
chosen at tunnel plants to convert the power derived from 
steam, water, electricity, or fuel gas into a form suitable for use in 
pneumatic rock drills, many factors enter into the problem of its 
selection. After the question of motive power and capacity, the 
type of the compressor is, perhaps, the next thing to be consid- 
ered. The methods of regulation under varying load likewise 
deserve attention. And, finally, the devices and accessories for 
preventing or neutralizing the effects of heat produced during 
compression and for removing moisture from the air bear directly 
upon our problem. 

The most familiar types of air compressors consist essentially 
of a cylinder in which air is subjected to pressure by a moving 
piston. Automatic means are provided to insure the admittance 
of free air and its delivery after compression, and the momentum 
of a fly-wheel is required to equalize the irregular demands of 
the piston for power. When stfeam or internal combustion 
engines are the prime movers they are usually, though not neces- 
sarily, incorporated with the compressor, the power and air 
pistons being connected by a common piston rod or engine 
shaft. Where water or electricity is em^ployed, the power is 
usually developed in separate motors and transmitted to the air 
compressor by a belt, the fly-wheel of the compressor in this 
case serving also as a pulley; but there has arisen lately a grow- 
ing demand for the '' direct-connected" electrically driven 
machine in which the electric motor forms an integral part of 
the compressor, the armature serving as a fly-wheel. Such 
machines are now suppHed by all the leading manufacturers. 
^'Direct-connected'' water-power driven air compressors are 
also obtainable in which the water-wheel carrying the buckets or 
vanes performs the additional function of fly-wheel for the com- 

80 



AIR COMPRESSORS 81 

pressor. Air compressors of an entirely different type, operating 
on the principle of the reverse turbine, have recently been placed 
on the market. They are especially adapted to take advantage 
of the high rotative speed of electric motors and steam turbines. 
Although the Taylor hydrauHc system is, strictly speaking, an 
air compressor, it has been described somewhat in detail as a 
means of utihzing water-power; since its use is ordinarily con- 
fined to units too large for tunnel work, it will not be discussed 
further. 

POWER REQUIRED 

Although the kind of motive power is generally predetermined, 
in designing a given plant, by local conditions, the amount of 
power required for this purpose is worthy of brief discussion. 
E. A. Rix is authority for the statement* that, in compressing 
air from atmospheric pressure to 90 or 95 pounds, f 20 brake horse- 
power must be dehvered at the fly-wheel shaft of a reciprocating 
compressor for every 100 cubic feet per minute of piston dis- 
placement. This figure is deduced as the average result of a 
number of tests of air-compressor plants, comparing the capa- 
bilities of almost every kind of compressor with the actual 
power required to operate them. He also states that the figures 
given in trade catalogues for the amount of power required in 
compressing air are usually somewhat lower than this value, but 
it must be explained that such figures are theoretical and do not 
take into consideration the mechanical or volumetric efficiencies 
of the compressor. The following tables are computed from the 
catalogues of two leading manufacturers for a popular type of 
compressor in each case and show^ the rated brake horse-power 
per 100 cubic feet cylinder displacement, where the final gauge 
pressure is 100 pounds. 

* Address before the Mining Assoc, Univ. of Calif., February 19th, re- 
printed Compressed Air Magazine, June, 1906, p. 4894. 

t Throughout this book when air pressure is mentioned the figures given 
will be those above atmosphere, i.e., gauge pressure. In many books the 
pressures given are absolute, i.e., the pressure above vacuum, while in European 
works on the subject pressures are generally expressed in terms of atmospheres, 
which in this country would be liable to create considerable confusion. 



82 



MODERN TUNNELING 



RELATION BETWEEN REQUIRED BRAKE HORSE-POWER AND 

CAPACITY 



Compressor A 


Compressor B 




Brake Horse-Power 




Brake Horse-Power 




Required for Each 




Required for Each 


Capacity Cu. Ft. 


100 Cu. Ft. Dis- 


Capacity Cu. Ft. 


100 Cu. Ft. Dis- 


per Minute 


placement Com- 


per Minute 


placement Com- 




pressing to 100 lbs. 




pressing to 100 lbs. 


144 


18.7 


248 


193 


247 


18 


6 


338 


19 


2 


372 


18 


4 


537 


18 


I 


534 


18 


3 


680 


18 


I 


704 


18 


I 


873 


18 





1051 


18 





1056 


18 





1312 


17 


8 


1188 


18 





1692 


17 


7 


1414 


17 


9 


2381 


^7 


7 


1845 


17 


9 



It will be observed that these tables bear out the statement 
made by Mr. Rix, and that even in spite of the increased final 
pressure, the values are somewhat less than the one he proposes. 
They also show that in machines of large capacity proportion- 
ally less power is required. 

The following table, based upon published figures, shows 
the amount of power required or provided per 100 cubic feet 
of free air actually compressed at several turbo-compressor 
installations : 

POWER CONSUMPTION OF TURBO-COMPRESSORS 





' 


Rated H.P.of Motor or 


Actual H.P. Required in 






Engine per loo Cu. Ft. of 


Compressing loo Cu. Ft. 


Pressure 


Capacity in Cu. Ft. Free 


Free Air When Com- 






Air per Minute 


pressing to Stated 
Pressure 


Stated Pressure 


90 


4,600 


21.8 




118 


21,250 


18.8 


17. 


135 


20,000 




18.5 


170 


22,000 


18.2 





CAPACITY 

The capacity of compressors is rated in free air,* and in 
reciprocating machines is equally based upon speed and piston 
displacement — that is to say, the number of cubic feet of cyl- 
inder space swept by the piston each minute at the given speed. 

*Free air is air at 14.7 lbs. pressure (atmospheric), and at a temperature 
of 60° F. 



AIR COMPRESSORS 



83 



I 



This is not, however, the actual capacity, because there are 
unavoidable losses in volume due to clearance, piston speed, 
leakage, and expansion, the sum of which may amount to as 
much as 30 per cent, of the rated capacity in a single-stage 
compressor at 100 pounds pressure. The capacity of turbo- 
compressors is based on the amount of free air drawn into the 
intake per minute. Although some of the more carefully designed 
reciprocating compressors may give a volumetric efficiency as 
high as 90 per cent., for compressors such as are customarily 
employed in power plants for tunnels 80 per cent, is more likely 
to be nearer the figure. While the tables shown in manufacturers' 
catalogues of air drills are in the main fairly accurate for new 
drills, the air consumption is often greatly augmented as the 
parts become worn. Provision must be made also for leakage in 
the pipe line and for the air required by drill sharpeners, black- 
smith forges, and an extra small drill which is sometimes used for 
blocking and trimming. It is therefore most desirable to have the 
air compressors, as based upon catalogue rating, considerably 
oversized, and in tunnel practice this usually ranges from 100 to 
150 per cent. The following table shows a comparison between 
the rated compressor capacity and the catalogue air consump- 
tion for the drills employed in the heading at several tunnels : 



RELATION BETWEEN COMPRESSOR CAPACITY AND AIR CON- 
SUMPTION OF DRILLS 



Tunnel 



Carter 

Laramie-Poudre , 
Elizabeth Lake . 

Lucania 

Marshall-Russell 

Mission 

Rawley 

Snake Creek . . . 
Strawberry .... 



Compressor Cata- 




logue Values 






Capacity 


No. 


Speed 


Cu. Ft. 


in 


r.p.m. 


per Min. 


Heading 


150 


868 


2 


165 


602 


3 


160 


736 


3 


130 


544 


3 


175 


487 


2 


190 


247 


I 


175 


427 


2 


165 


680 


2 


175 


427 


2 



Drills 



Air Consumption 

from Catalogue 

Cu. Ft. per Minute 



230 at 

250 " 

185 " 

250 " 

200 " 

100 " 

190 " 

300 " 

300 " 



9,000 elev. 
8,000 
3,000 
8,000 
8,000 
1,200 
10,000 
6,000 
7,000 



Oversize 
of Com- 
pressor* 



280% 

140 

300 

120 

140 

120 

125 
40 



Not including drill sharpeners, forges, or leakage in pipe lines. 



84 MODERN TUNNELING 

The decrease in effective capacity of the compressor caused 
by leakage in pipe lines is in many cases not fully realized, and 
steps are not taken either to determine the amount of this 
waste or to prevent it. Where the compressed-air lines are con- 
structed with great care and covered so as to protect them from 
accident or from extremes of temperature, the loss by leakage 
may be slight or almost negligible; but where they are not well 
built or where they remain uncovered, the lines on the surface 
are exposed to injury from numerous causes — not the least of 
which being diurnal and seasonal variation in temperature — 
and those underground are apt to be struck by falling rock, 
derailed cars, etc. In such cases the leakage is likely to be a 
very considerable item, and the greatest care should be taken to 
test the- lines at short intervals to ascertain the amount of loss 
in order that whatever is necessary may be done to stop it. 
Where reciprocating compressors are used, driven either by steam- 
or water-power, it is an easy matter to ascertain the amount of 
leakage by simply closing all of the outlet pipes from the line 
and noting the number of strokes per minute necessary to main- 
tain the desired pressure; but where turbo-compressors are used, 
unless a very careful table has been compiled showing the output 
at different speeds and pressures, the leakage can best be ascer- 
tained by stopping the compressor when the receiver and lines 
are filled, allowing the pressure to drop to 50 per cent., let us 
say, then starting up the machine and noting the length of time 
required to bring up the pressure to the original point. While 
this does not give exact results, still it will furnish a useful, if 
not exactly correct, index to the rate at which the compressed 
air is escaping. Such a method of ascertaining the amount of 
leakage is so simple that it would seem that it ought to be in 
general use; but unfortunately it appears to be the habit of 
workmen, especially of the ''chain gang," to assume that all air 
lines are much more free from leaks than they really are. A few 
years ago at one of the large mines in the West which operated 
a great number of drills, drill sharpeners, and pumps by com- 
pressed air, it was found impossible to maintain the required 
pressure, and bids for a new and expensive compressor were 



AIR COMPRESSORS 



85 



called for, when it occurred to the management to test the 
pipe lines by the method above indicated, and it was discovered 
that I, IOC horse-power were required to supply the loss by leak- 
age. In this case the ''chain gang," instead of the machine 
shop, ''got busy," and in a week the leakage was stopped and 
the waste of air reduced to such a point that, instead of buying 
another compressor, one of the largest machines w^as shut down. 



TYPES 

Reciprocating air compressors may be divided into two 
general types: " straight-Hne " (sometimes called "tandem") 
and duplex. Either of them may be single stage where the air 
reaches its final pressure in one cylinder, or multi-stage where 
only a portion of the compression takes place in the first cylinder 
and is finally completed in a second, third, or even fourth 
cylinder. 

Straight-line 

In the tandem compressor, if it be driven by steam or an 
internal combustion engine, the power and air cyHnders are 
placed tandem-fashion along a common piston rod, and the 




Fig. 12. Section through a single-stage straight-line compressor in which the 
power cyhnder is an internal combustion engine using gasoline fuel. 

power is thus applied in a straight line. (See Figures 12 to 14.) 
The fly-wheels, of which there are usually tw^o, may be at either 



n 




c/) 



88 



MODERN TUNNELING 



end or between the cylinders and are connected to the piston 
rod by a cross head and ordinary connecting rods. If it be driven 




Fig. 15. bin^lu-blage, power-driven compressor. 

by electricity or water, practically the only change is the omission 
of the power cylinder. (See Figures 15 and 16.) 

Duplex 

A duplex compressor consists of two tandem compressors 
placed side by side, having a fly-wheel between them on a com- 




FiG. 16. Belt-driven, straight-line, two-stage compressor. 

mon shaft. The two sides are connected to the fly-wheel shaft by 
cranks set at 90° so that when one side is encountering maximum 
resistance, the other is working under the Hghtest load. There 
are many different combinations possible with the duplex type. 
The steam cylinders * may or may not be compounded (see 

* Internal combustion engines have not as yet been applied to this type 
of compressor. 




Fig. 17. Duplex, simple-steam, two-stage air compressor. 




c 

3 

o 
a- 

S 
o 

u 

"a 

3 

Q 



AIR COMPRESSORS 



91 



Figures 17 and 18), and the air cylinders may be single, or 
multi-stage. (See Figures 17 and 18.) Again the steam 
cylinders may be omitted and the power transmitted to the 




Fig. 19. Duplex, belt-driven, two-stage air compressor. 

machine by a belt (see Figure 19) or by a directly connected 
motor. (See Figure 20.) 

Turbo-compressors 

The turbo-compressor operates upon the principle of a re- 
versed turbine in which air, instead of water or steam, is the 
fluid acted upon, and it consists essentially of a revolving im- 
peller (not unlike that of some forms of centrifugal fans) sur- 
rounded by a set of stationary discharge vanes supported in a 
suitable casing (see Figure 21). It is the function of the discharge 
vanes to recover the major portion of the energy which exists 
in the air as velocity upon leaving the impeller, and which is 
roughly almost one-half of the total energy suppHed from the 
driving machine, by converting this velocity into available press- 



AIR COMPRESSORS 



93 



ure. In the centrifugal fan, 
there being no such vanes, this 
energy is lost as heat produced 
by eddies and friction, hence it 
is not difficult to see the rea- 
sons for the higher efficiency of 
the new machine. Single-stage 
turbo - compressors are em- 
ployed chiefly in connection 
with blast furnaces, cupolas, 
etc., and could be used for 
mine ventilation; but where a 
high pressure is required, such 
as that needed for the opera- 
tion of rock drills and other 
pneumatic machinery, a num- 
ber of impeller units are 
mounted on a common shaft 
operating in series within a 
common casing, the air upon 
leaving the first set of dis- 
charge vanes being conducted 
to the intake of the second 
impeller, and so on. Com- 
pressors producing 170 pounds 
pressure and having as many 
as 29 stages have been con- 
structed, but where so many 
stages are employed the im- 
pellers are usually mounted in 
groups of from four to ten. 

The manufacture of turbo- 
compressors is just beginning 
in this country, but they have 
been in use for several years in 
Germany, where their design 
and manufacture have already 




94 MODERN TUNNELING 

reached a high degree of perfection. The first large machine of 
this kind was built in 1909 for the Reden mines near Swar- 
brucken. It is driven by i ,000-horse-power, mixed pressure, 
steam turbine at 4,200 revolutions per minute, and compresses 
4,600 cubic feet of free air per minute to a gauge pressure of 90 
pounds to the square inch. Quite recently, six motor-driven 
compressors of this kind were built in Germany for the Rand 
mines in South Africa. Each of these six machines is operated 
by two 2,000-horse-power synchronous motors running at 3,000 
revolutions per minute. The compressors have a rated capacity 
of 21,250 cubic feet of free air per minute at 68° F. to 118 pounds 
pressure per square inch. In a test, when compressing 23,750 
cubic feet of free air per minute to 100 pounds pressure, the 
energy of consumption per hundred cubic feet of free air was 17 
horse-power and the highest isothermal efficiency obtained was 
67.04 per cent. The first large compressor built in this country 
went into service in May, 191 1, and has been in continuous oper- 
ation ever since. This machine (figure 22) is driven by a steam 
turbine at 4,700 revolutions per minute and has a capacity of 
3,500 cubic feet of free air per minute delivered at a pressure of 
105 pounds per square inch. 

It is of course not possible, nor is it within the proper scope 
of this volume, to describe all the numerous makes of air compres- 
sors; for such material the reader is referred to the trade cat- 
alogues issued by the various manufacturers, who will be glad 
to supply this information, and whose experts are prepared to 
render any assistance possible in the selection of a compressor. 

COMPARISONS 

The chief advantages of the straight-line compressor are 
that it is strong, simple, compact, and easily installed. It is 
usually self-contained, being mounted on a single bed plate, 
and requires relatively inexpensive foundations. The frictional 
losses in a good machine of this type are not large and, at or near 
^ull load with moderate pressures, it may have a fairly good power 
economy. These features make it advantageous for less access- 
ible plants or those of a more or less temporary character. 





Fig. 22, Turbo-compressors. 



96 MODERN TUNNELING 

A great advantage of the duplex type, on the other hand, is 
the faciHty with which either steam or air cyHnders may be 
"compounded" without increasing materially the number of 
parts. This makes it possible for the duplex type to take 
advantage of the great saving in power resulting from com- 
pound steam cylinders, as well as the economy resulting from 
two-stage air compression. Practical experience with the two 
types of machines fully confirms the theoretical investigations 
of their comparative efficiency, and carefully conducted tests 
extending over long periods of time have established the eco- 
nomical superiority of the duplex type. In this type, also, if 
properly designed, the mechanical losses through friction, etc., 
are but little greater, if any, than in the straight-Hne compressor, 
and it is much more easily regulated under varying loads. Most 
manufacturers are now making duplex compressors with a sub- 
stantial sub-base, giving the machines a strength and rigidity 
comparable with the other type, reducing the expense of foun- 
dations, thus meeting some of the conditions which have until 
recently been so much in favor of the straight-line type. The 
result is that, with perhaps a half-dozen exceptions, the air com- 
pressors at tunnel plants examined were of the duplex type. 

The entire absence of valves, reciprocating parts, and sliding 
friction in turbo-compressors, together with their freedom from 
vibration, their high capacity in proportion to weight and to 
floor space occupied, and their ability to take advantage of the 
high rotative speeds of electric motors and steam turbines, are 
certain to bring these new aspirants for engineering favor into 
general use. Using live steam, condensing or non-condensing 
turbine-engine turbo-compressor units are quite able to compete 
successfully with the very highest grades of reciprocating-engine 
compressor plants, and they can be operated successfully with 
exhaust steam from engines, pumps, or other apparatus, which 
forms one of the cheapest possible sources of power — because in 
utilizing steam which would otherwise go to waste, practically 
free fuel is obtained. Another advantage, and one that might 
easily be overlooked, is the fact that it practically eliminates 
the danger of explosions in air receivers and pipe lines. In piston 



AIR COMPRESSORS 97 

compressors lubrication must be supplied to the inside of the 
cylinder in order to protect it from the friction of the sliding 
piston; there is, therefore, every opportunity for the oil (which 
becomes finely divided in this process) to commingle with the 
air as it is being compressed and to be carried with it into the 
receiver. But with the turbo-compressor the only surfaces re- 
quiring lubrication are those of the bearings to which the air 
being compressed has no access. When an electric motor or water- 
wheel is the source of power, the ease with which the turbo- 
compressor may be connected to either of them, thereby avoid- 
ing all loss due to speed reduction and friction, renders this a 
most desirable combination. The turbo-compressor is readily 
adapted to automatic control and may be regulated for the 
delivery of a constant volume or constant pressure as required. 
Its efficiency is maintained over a wide range of load within a 
few per cent, of the maximum, and the efficiency does not decrease 
with continued service. There is, therefore, every reason to 
expect that turbo-compressors will come into general use in the 
near future. 

REGULATION 

Steam Driven 

Although, when steam driven, a change in load with any 
type of machine results in a variation of speed, this works more 
to the disadvantage of the straight-Hne compressor, especially 
with high air and steam pressure, because this type will not run 
satisfactorily at low speeds, the momentum of the fly-wheel 
not being sufficient to carry it past dead centers. To avoid stop- 
page, either the steam cut-off must be lengthened (in which case 
there is a loss of steam as the machine speeds up under increasing 
load) or there must be a fixed limit below which the steam is not 
decreased, and when the demand for compressed air falls below 
that supplied regularly by the machine the excess must be per- 
mitted to escape through a safety valve. Both of these cases 
entail loss of power. For this reason the straight-line compressor 
cannot operate economically much below the Umit of 40 per cent, 
of full load. 



98 MODERN TUNNELING 

In this matter of regulation the duplex, steam-driven machine 
has an unquestioned advantage over the straight-line machine. 
The quartered cranks, in addition to minimizing strains and 
reducing extremes, enable one cylinder to come to the help of the 
other just at the time when that help is most beneficial, and, a 
quarter of a revolution later, the favor is returned. There can 
be no dead center, and the machine will run so slowly as hardly 
to turn over if the compressed air in the receiver is not being 
drawn upon, and will speed up rapidly as there is an increased 
demand for air, doing it without any change in the cut-off. The 
duplex machine, therefore, has the same steam economy over 
the full range of load, without any loss of compressed air at the 
safety valve. 

With the turbo-compressor when steam-turbine driven, the 
regulation is merely a matter of controlling the amount of steam 
admitted to the turbine. 

Water Driven 

The regulation of compressors driven by impulse wheels may 
be accomplished by several methods, among which may be men- 
tioned the deflecting nozzle, the needle nozzle, and the cut-off. 
The deflecting nozzle is provided with a ball and socket joint 
and is controlled by air receiver pressure in such a manner that 
a portion of the stream of water may be shifted on or off the 
buckets of the wheel, thus increasing or decreasing the amount 
of power developed to correspond with varying loads. A steel 
plate may be made to accomplish the same effect by deflecting 
the stream of water, the nozzle in this case remaining stationary. 
The needle nozzle is merely a discharge valve in which a conical 
needle is inserted or withdrawn from an orifice, thus diminishing 
or increasing the amount of water passing through. The cut-off 
also regulates the water quantity by a change in the discharge 
area, produced by the shifting of a plate which fits tightly over 
the nozzle tip. The deflecting devices are capable of controlling 
rapid variations in power demand, but are, of course, wasteful of 
water, while just the reverse is true of the other types. At tunnel 
plants, however, water economy is rarely an essential consider- 



AIR COIVIPRESSORS 99 

ation while variations in load are frequent and sudden ; the de- 
flecting devices are therefore most suitable. 

Electrically Driven 

The volume of air compressed in any reciprocating machine 
varies with the number of strokes per minute made by the 
piston; in the turbine compressor it is dependent upon the rota- 
tive speed. In electrically driven reciprocating compressors, 
whether directly connected or belted to a motor, the speed is 
necessarily reasonably constant and cannot be varied to meet 
fluctuating demands for air; and since economy obviously for- 
bids the discharge of excess compressed air through a safety 
valve, "unloaders" must be provided to overcome the difficulty. 

Ufiloaders. — The more common method is to limit the amount 
of air admitted to the machine. This type of unloader consists 
of a valve in the free-air intake pipe controlled by the pressure 
in the air receiver, which throttles the admission of air when the 
load is Kght, and allows more of it to enter when the demand for 
air increases. This device may be employed successfully with 
turbo-compressors, but with reciprocating machines it never- 
theless has its drawback, because when running with a partially 
throttled inlet, the smaller amount of air drawn into the cyhnder 
is rarefied and on the return stroke of the piston is consequently 
compressed through a greater range of pressure, giving rise to 
higher temperatures than ordinary and they may reach unsafe 
limits, especially where the terminal pressures are great. This 
is not so important with turbo-compressors because the temper- 
atures never become so high as they do in reciprocating machines. 

On some piston compressors an unloader of almost an ex- 
actly opposite type is employed and consists of a device for 
holding the intake valves open whenever the air pressure reaches 
a predetermined point. 

In one type of unloader for reciprocating machines the excess 
air is forced automatically into clearance tanks, the process 
being controlled by a predetermined receiver air pressure. Fig- 
ure 23 gives a diagrammatic representation of this de\dce. Under 
normal full load the controller is inoperative, but when working 



100 



MODERN TUNNELING 



at partial capacity a portion of the compressed air is forced into 
the tanks instead of going through the discharge valve, thus 
reducing the output of the compressor. On the return stroke 
this air expands, returning its stored energy to the piston. There 
are eight tanks in all, and four equal and successive unloading 
stages are possible by throwing in respectively two, four, 
six, or all of the tanks. The regulation is said to be unaccom- 
panied by shock due to sudden variations in load, and heating 




Fig. 23. Diagrammatic cut of clearance controller. 



caused by the compression of rarefied air is avoided — in fact, 
since there is a slight radiation from the clearance tanks, the air 
is probably returned to the cylinder slightly cooler than when 
it left. 

Another method of unloading is by holding open the discharge 
valves of the compressor, permitting compressed air instead of 
free air to fill the cylinder as the piston retreats, and thus bal- 
ancing the pressure on both sides of the piston. Although this 
unloads the compressor completely, it has a very serious draw- 
back. As the load is resumed the balance of pressure is dis- 
turbed, one side of the piston being subjected to something less 



AIR COMPRESSORS 101 

than atmospheric pressure, while the opposite side is exposed to 
the full pressure of air in the receiver, the difference in pressure 
being thrown on the piston instantly and maintained throughout 
the entire stroke. As a result, serious strains are placed upon 
the structure of the compressor which prohibit the use of this 
unloader except in the smaller sizes. Still another type releases 
the partially compressed air during its passage from the low- to 
the high-pressure cylinders, but little can be said for this method 
except that it is not quite so wasteful as releasing high-pressure 
air. 

HEAT 

Heat Produced 

Heat is produced during the compression of air and the rise 
in temperature is largely dependent upon the difference between 
the initial and final pressure. For instance, if air at 60° F. be 
compressed in a single stroke from atmospheric pressure to 
100 pounds gauge, the temperature attained would be 485° F., 
assuming no loss by radiation during the process. On the other 
hand, under the same conditions, if the final pressure were but 
25 pounds gauge, the air would be heated only to 233° F., and if 
it were then cooled again to 60° and further compressed from 
25 pounds to 100 pounds gauge the final temperature would 
approximately be 250° F. The effect of the increase in tempera- 
ture is to cause the air to expand to a larger volume, and hence 
more work is required to compress it. If the air could be used 
at once to operate a motor, before any of the heat escapes through 
radiation, etc., this work could be obtained again from the air; 
but since in mining work the heat is almost without exception 
entirely dissipated in the pipe line before the air reaches the 
drills, the production of heat during compression entails a serious 
loss of power. 

Dangers of High Temperatures 

Aside from the item of power waste, the temperature reached 
during compression has an important bearing on the question of 



102 MODERN TUNNELING 

explosions in air lines. It can readily be imagined that if the dis- 
charge valves are not working properly and some of the highly 
heated compressed air is allowed to re-enter the cyHnder with 
the fresh intake air, compression may begin at a temperature 
much higher than normal, in which case, even with two-stage 
machines, the final temperature of the compressed air may be 
gradually built up from 250° to 500°, 600°, or even higher. It 
is often sufficiently high to volatilize lubricating oil, the vapors 
of which, mingling with the air, may be in proper amount to 
form an explosive mixture. If the temperature then becomes 
high enough to ignite this mixture, an explosion inevitably 
results. There have been numerous instances where this has 
actually occurred. 

Removal of Heat 

The ideal way to prevent the evil effects of heat would be 
to devise some means of removing it from the air as fast as 
produced during compression. Such a course is unfortunately 
impossible of attainment in practice, but various means have 
been invented which partly accomplish the result. A famiHar 
one is to surround the cylinder with a jacket of cooHng water, 
the piston also being sometimes cooled in this way. But when 
one considers that air is a very poor conductor of heat and that 
at the time when it. is hottest it occupies but the minimum 
volume in one end of the cyhnder, and even then but for a short 
space of time, it will readily be seen that this method cannot 
be very effective. In some modern compressors the inlet 
valves are placed in the piston and the discharge valves in the 
ends of the cylinders instead of in the heads, thus permitting 
the latter to be fully water-jacketed, a practice which is to be 
most highly commended. As water- jacketing is the only means 
used to cool the air during single-stage compression, it is not 
surprising that such machines are not economical of power. 

In two-stage compressors, however, a portion of the heat is 
actually removed during compression. The air is only partially 
compressed in the first cylinder, perhaps to 25 pounds gauge, 
and the heat produced is practically all removed during the 



AIR COMPRESSORS 103 

passage of the air through an intercooler in its way to the 
second cylinder, where the final pressure, of perhaps loo pounds, 
is attained. By removing the heat in the inter-cooler, the 
temperature of the air is kept much lower than with single-stage 
compression, hence there is less expansion of the air to be over- 
come, resulting in a consequent saving of power. In a properly 
designed two-stage machine compressing to loo pounds gauge, 
this saving of power is approximately 13 per cent., and it increases 
with the higher terminal pressures. If the pressure is less than 
80 pounds, the saving is hardly great enough to be a serious 
consideration and single-stage machines are customarily em- 
ployed in such cases, but for pressures higher than 100 pounds 
two-stage compression is imperative, because of the high temper- 
atures that are otherwise produced. As shown by the following 
table, the pressure ordinarily employed in tunnel plants ranges 
from 80-120 pounds, averaging about 100 pounds. 

Compressed Air Pressures at Different Tunnel Plants 

Carter 112 Marshall-Russell no Roosevelt no 

Central 120 Mission 100 Siwatch 80 

Gold Links 100 Moodna 95-100 Snake Creek. ... no 

Gunnison 90 Newhouse no Stilwell 100 

Laramie-Poudre 120 Nisqually 90-95 Strawberry 85 

Mauch Chunk.. . 100 Rawley 100 Utah Metals. ... no 

Los Angeles Raymond 90 Walkill no 

Aqueduct 100 Rondout 100 Yak 90 

Lucania 115 

Because of the many stages required with turbo-compressors 
when delivering air for use in drilling, the difference between the 
pressures of the air on entering and leaving any one stage is 
extremely small compared with that of two-stage reciprocating 
machines. Hence the resulting increase of temperature in any 
one step is not great, and it is possible to remove the compara- 
tively small amount of heat generated effectively by the use of 
a suitably designed water-jacket. Some idea of the efficiency 
obtainable with such a cooKng system may be had from the 
fact that the air delivered into the receiver at 105 pounds 



104 



MODERN TUNNELING 



pressure from the turbo-compressor illustrated in Figure 22, 
page 95, has a temperature of only 120° F. 

Intercooling 

The efficiency of two-stage compression is largely dependent 
upon the intercooler. It is an essential part of this type of 
machine, and usually consists of a shell, generally cyKndrical in 
shape, containing a number of pipes, similar to those in a tubular 
boiler, through which cold water is made to circulate. See 
Figure 24. The heated air from the low-pressure cylinder enters 



Water 

outlet 
pipe, 




JJTatej drain 



Connection foe 
low-pressure 
air cylinder. 



Fig. 24. Typical Intercooler. 



near one end, passes through the nest of tubes, its passage being 
obstructed by baffle plates to insure the maximum contact 
between air and cooling surface, and is delivered at much lower 
temperature to the high-pressure cylinder at the other end. 
The success of the intercooler depends upon several considera- 
tions. In order that the least dependence need be placed upon 
the heat conductivity of the air itself, which is notably poor, the 
intercooler must subdivide the air completely, and insure that 
the maximum amount of it is thrown in contact with the cooling 
surfaces. This is accomplished by properly spaced water- tubes 
and baflie plates. At the same time the cross-section of the 
cooler must not be too small, in which case the velocity of the 
air past the cooling surface would be so great that sufficient 
time would not be allowed for the water to absorb all the heat. 



AIR COMPRESSORS 105 

It is very desirable also to have the water and air flow in opposite 
directions in order that the final cooling of the air may be effected 
by the entering, and consequently the coldest, water. Theoreti- 
cally, the cooling surface should be sufficient to absorb all the 
heat in the air passed over it, reducing the temperature to the 
point at which the .air entered the low-pressure cylinder, but 
due possibly to mechanical difficulties, even in good practice, 
intercoolers usually fail to do this within five or ten degrees, 
while even 30 or 40 degrees are not unusual. 

Moisture 

The intercooler assists also in removing water from the air. 
Normal atmosphere always contains at least some water vapor, 
but for any combination of relative volume and absolute temper- 
ature, air is incapable of absorbing more than a certain amount 
of water vapor. This maximum at 60° F. and 14.7 pounds 
pressure is .0137 ounce, while under the same pressure and at 
32° F., air can hold but .0046 ounce and at 0° F. but .0011 
ounce. In the air compressor both of these factors of volume 
and temperature are suddenly and violently disturbed. The 
water vapor in the air would be released were it not for the fact 
that as the volume is reduced (a process which would ordinarily 
decrease the capacity of the air for moisture) the temperature 
is greatly raised at the same time, increasing the water-carrying 
capacity of the air; the increase in capacity for moisture, caused 
by the high temperature, being greater than the decrease due 
to reduced volume and no water is precipitated. But as the 
air passes through the intercooler the temperature is lowered 
greatly without a corresponding increase in volume, and the 
air is forced to give up its water. It is precipitated in such a 
finely divided state, however, that it requires some time to 
settle; for that reason only a portion of it can be collected in the 
intercooler and drawn off through drains provided for that 
purpose, the remainder being swept along with the air to the 
higher-pressure cylinder and revaporized by the tem^perature 
there attained. 



106 MODERN TUNNELING 

ACCESSORIES 

Precoolers 

Cooling the air before its admission into the air compressor 
also assists in removing some water from it, and there are a 
number of devices for this purpose. One precooler described 
in the Engineering and Mining Journal * is a home-made affair 
consisting simply of a number of odd pipes set between two 
wooden boxes. The pipes are wrapped with cloth and water is 
arranged to drip on them constantly, so that the air is cooled 
by evaporation as it is drawn through them from one box to 
the other on its way to the compressor intake. At a plant in 
Johannesburg the air for the compressors is obtained through a 
subway leading to the center of a building with air-tight roof 
and floors, and with walls consisting of constantly wetted cocoa 
matting. At another plant a similar structure was used in which 
the sides and roof were covered with burlap both inside and out. 
A cooler of this type also filters dust and grit which might seri- 
ously injure the cylinder or piston of the compressor, and can- 
not be too strongly recommended in dusty situations. Pre- 
cooling the air also increases the capacity of the compressor, 
because the cooler air occupies less space than when it is heated, 
hence a larger actual arnount of air will be drawn into the 
cylinder and compressed at each stroke. 

After-cooling 

The after-cooler, t although it is not generally employed in 
tunnel plants, by cooling the air at once after it comes from the 
high-pressure cylinder, also precipitates some of the water vapor, 
but at the same time it reduces the volume of the air and practi- 
cally eliminates the danger of explosion in the air line. Although 
the air gives up its water vapor in the cooler because of the de- 

* November 27, 1909, p. 108 1. 

t In design and principle the after-cooler is practically the same as an 
intercooler, and it is usually placed between the compressor and the air 
receiver. 



AIR COMPRESSORS 107 

crease in temperature, it is usually in so finely divided a state 
that all of it does not at once fall out, part being swept along with 
the air and deposited both in the air receiver and in the pipe line. 
There should, therefore, be provision for draining this water at 
some low point. The amount of the reduction in volume is 
somewhat speculative and probably not a serious consideration. 

Air Receivers 

The air receiver,* according to the popular notion, is supposed 
to perform the functions of storing, cooHng, and drying air, 
together with equaUzing irregularities in its production and use, 
but it is more than probable that in actual practice it accom- 
plishes these results, wdth the exception perhaps of the last one, 
very inefficiently. When one takes into consideration the fact 
that the receiver ordinarily installed in tunnel plants rarely has 
a capacity greater than one minute's run of the compressor, it 
will be seen that it cannot possibly furnish any great amount of 
storage space. Then, too, since the air in the receiver is being 
renewed each minute when the compressor is in operation the 
velocity of the air through the receiver must be enough to pre- 
vent any great amount of cooHng. There will, of course, be some 
radiation of heat from the air near the shell, but this is small 
compared to the heat in the mass of the air in the center of the 
receiver, so that the air leaves with a temperature but sKghtly 
lowered, if at all, below that at which it entered. And further- 
more, since there is practically no cooling of the air, there can 
be no great precipitation of water vapor. As a matter of fact 
this is the case in practice, for, although most air receivers are 
provided with a drain of some sort, only a ridiculously small 
amount of water is ever drawn off. On the other hand, instead 
of cooKng, the air receivers have actually in some instances 
become combustion chambers. Oil and grease in time collect on 
the inside of the shell and may become ignited if the tempera- 
ture of the air becomes high enough. Together with the pipe 

*The air receiver consists simply of a cylindrical shell of steel provided with 
inlet and outlet pipes and usually a safety valve. 



108 MODERN TUNNELING 

line, which storage space may be considered as an auxiliary, the 
receiver does assist greatly, however, in equalizing the pulsations 
not only of the air dehvered from the compressor but also of 
that used by the drills, and in this way it reduces strain on the 
structure of the compressor. By regulating the flow, it does not 
permit the air to attain a high velocity in the pipes even irregu- 
larly, and hence power is saved since the friction losses increase 
greatly with the velocity. To secure the maximum benefit from 
this factor, a second receiver is often installed as near as possible 
to the place where the air is to be used. In this case the second 
receiver assists materially in maintaining a steadier air pressure 
at the drills. A tubular boiler, which it is often possible to buy 
cheaply at second-hand, makes an excellent receiver and a very 
efficient cooler. With a vertical tubular boiler it is only neces- 
sary to remove the fire and ash doors to provide for ventilation, 
while a horizontal tubular boiler should be placed on an incline 
sufficiently steep to insure a rapid draft of outside air through 
the flues. 

Drains 

Since practically the entire cooling of the air after leaving 
the compressor takes place in the pipe fine, it is here that most 
of the water is precipitated and causes serious inconvenience in 
several ways. During cold weather, through continued deposi- 
tion and freezing, the pipe fine may become closed altogether or 
so restricted as to cause serious drop in pressure or loss of power. 
Or the water getting into the exhaust from the driUs not 
uncommonly prevents their operation through freezing at the 
low temperature of the expanded air. The obvious remedy is 
to remove the water, which is done by draining the low places 
in the fine where the water collects. This can be accompfished 
automatically by the use of any good float design steam trap, 
but where the pipe is exposed to low temperatures the trap 
should be placed in a small pit or otherwise protected to prevent 
freezing. Where necessary, further provision for the efiminaticn 
of moisture from the compressed air and water from the pipes 



AIR COMPRESSORS 109 

can be had by placing in the Hne any high-class standard steam 
separator, fitted with an automatic trap as described above. 

CONCLUSIONS 

In conclusion, let us sum up briefly the factors which enter 
into the problem of selecting an air compressor. The power 
required for both reciprocating and turbine machines is approx- 
imately i8 to 20 brake horse-power for every 100 cubic feet of 
free air compressed to 100 pounds gauge. The values given in 
trade catalogues for reciprocating compressors are generally a 
little below this figure, but it is a safe one to use in estimates. 
Such compressors ordinarily have a volumetric efficiency of 
approximately 80 per cent., and since they are rated on the 
basis of free air and since it is necessary to make allowance for 
loss due to clearance, etc., provision for increased air con- 
sumption above the catalogue rating for drills as they become 
worn, and for that used in sharpening machines and forges, 
must also be made with either reciprocating or turbine machines, 
and it is advisable to select an air compressor considerably over- 
size. In practice the amount of oversize, based upon drills 
only, ordinarily ranges from 100 to 150 per cent. Of the two 
types of reciprocating compressors the duplex is preferable to 
the straight line (in spite of the latter's simplicity and easier 
installation) because of the former's more economical and 
efficient use of power and the faciHty of its regulation, especially 
when steam driven and with high pressures. Since the air pressure 
at tunnel plants is rarely below 80 pounds, and in three out of 
every four it is 100 pounds or greater, two-stage compression 
is desirable because of its economy of power, if not indeed 
imperative because of the air temperatures that might other- 
wise be attained. Although the manufacture of turbo-compres- 
sors is just beginning in this country, they possess a number of 
advantages, especially for use with steam turbines and other 
rotary engines operating at high speeds, which will doubtless 
lead to their more general use in the future. Their development 
should therefore be closely watched. Steam-driven compressors 



110 MODERN TUNNELING 

are regulated by varying their speed; but since in some power- 
driven machines the speed is necessarily constant, other means, 
of which the throttle inlet and the clearance controllers are the 
two most used, must be provided for that purpose. Heat is 
produced during compression and by expanding the air causes 
loss of power. Some of this loss is obviated in two-stage compres- 
sion by removing the heat during its passage through an inter- 
cooler between the cylinders. The numerous stages in the 
turbine machine enable this heat to be removed effectively by 
water- jacketing in this type of compressor. Another evil attrib- 
utable to this heat is the danger from the explosion of volatilized 
lubricating oils; but in the turbine machine this danger is elim- 
inated because there are no sliding surfaces to require lubrica- 
tion. Among the accessories which are designed to prevent or 
neutralize the effects of heat in piston machines are the pre- 
cooler, the intercooler, the after-cooler, and the air receiver. 
The last mentioned also equalizes the pulsations of the air and 
reduces friction losses. These devices assist, too, in freeing the 
air from water, which often causes serious inconvenience. The 
major portion of the water is deposited in the pipe line, however, 
where provision must be made for its removal. 



^ 



CHAPTER VI 

VENTILATION 
MACHINERY 

Either blowers or fans are employed ordinarily for ventilat- 
ing tunnels and adits. In machines of the first type, a certain 
amount of air is trapped every revolution between the impellers 
and the enclosing casing, and has no means of escape (to omit 
from consideration a small amount of leakage) except through 
the exhaust pipe (see Figure 25). For this reason they are 





Fig. 25. Diagrammatic cross-sections illustrating the action of pressure 

blowers. 

often styled '' pressure" blowers and "positive blast" machines. 
Figure 26 shows one of these blowers in operation on the Los 
Angeles aqueduct. 

Where fans are employed in tunnel ventilation they are, 
almost without exception, centrifugal — the famiUar propeller 
form similar to the ordinary desk fan being rarely used. In ihe 
centrifugal fan the air enters near the center, traveling in a 
direction approximately parallel to the axis of the shaft, and is 
forced by the centrifugal action of the rapidly revolving blades 
toward their periphery, where it is collected and discharged. 
There are many modifications of this design, with the intention 
of preventing loss of efldciency through friction as the air strikes 

111 



112 



MODERN TUNNELING 



the back plate and changes direction, or to prevent eddies, etc., 
due to the greater density of the air at that point caused by its 
momentum upon entering the fan. 

Turbo-compressors in which, by the adoption of one or two 
or even several stages, air can be deHvered at any required 
pressure, have been employed as blowers for blast-furnace and 
foundry work at a number of places. The capacities of those 
manufactured for this purpose thus far are too great for the 
requirements of tunnel work, but their greater efficiency as 




Fig. 26. Ventilating blower used on Los Angeles Aqueduct. 



compared with centrifugal fans and the possibility of designing 
them to secure any required pressure will doubtless soon lead 
to their being made in sizes suitable for tunnel work, where 
they should have a large field. 

At one tunnel a certain amount of vitiated air was removed 
from the heading by the use of a jet of highly compressed air 
which was directed into the ventilating pipe; but this method, 
in addition to being expensive, is inadequate as well, and is, 
therefore, not to be advised, except as a temporary expedient 
and for short distances. On short levels and cross-cuts, how- 
ever, or on larger work pending the installation of more expensive 
and efhcient machinery, jet blowers can often be used to good 



VENTILATION 



113 



advantage. They can be operated by either compressed air 
or water under pressure, and, while far from being as efficient 
as the mechanical types of ventilating machinery, will in many 
cases perform an extremely useful function. Jet blowers can 
frequently be used with good results to move large volumes 
of air for short distances against low frictional resistances, and 
their extreme economy in first cost makes them an excellent 
accessory in preHminary work. 



DIRECTION OF CURRENT 

The fan or blower ordinarily installed for tunnel work may 
be made, by a proper adjustment of the ventilating pipe, to 
exhaust the air from or deliver it to the heading. One of the 
chief advantages of the first method is that the dangerous gases 
and smoke produced in blasting are promptly removed from 




Fig. 2']. Arrangement of gates and pipe for changing direction of 
ventilating current. 

the tunnel, and it is therefore unnecessary for the workmen 
to pass through a thick bank of smoke which would otherwise 
travel very slowly to the portal. On the other hand, when fresh 
air is blown in, it passes very much faster through the pipe and is 
cooler and fresher than if it had worked its way slowly in through 



114 



MODERN TUNNELING 



the tunnel or adit and become heated from contact with the 
walls and contaminated by odors from the track; the men, 
therefore, feel more comfortable and are able to do better work 
when this method is employed. The advantages of both methods, 
however, may be readily obtained by an arrangement of pipes 
similar in principle to the one shown in Figure 27, which permits 
the air to be exhausted for a few minutes after blasting, by 
opening gates a and h and closing c and d (assuming the 
current through the fan or blower to be in the direction of the 
arrow), while at other times, by reversing this arrangement, air 
may be forced into the heading. The following table shows the 
direction of the air current at various tunnels visited, from which 
it may be seen that, almost without exception, it is customary to 
exhaust the smoke, after blasting at least, although at many places 
the ventilating current is reversed at other times. This arrange- 
ment is reported as giving excellent results, and its use is strongly 
recommended. 

DIRECTION OF AIR CURRENT AT VARIOUS TUNNELS 



Tunnel 

Carter 

Central ' . . 

Gold Links 

Gunnison, East Portal 
Gunnison, West Portal 

Laramie-Poudre 

Lausanne 

Los Angeles Aqueduct, 

Elizabeth Lake 

Little Lake 

Grapevine 

Lucania 

Marshall- Russel 

Mission 

Newhouse 

Nisqually 

Rawley 

Raymond 

Rondout 

Roosevelt 

Siwatch 

Snake Creek 

Stilwell 

Strawberry 

Utah Metals 

Walkill 

Yak 



Ordinarily 



After Shooting 



Exhaust 

Exhaust 

Exhaust 

Exhaust 

Blast 

Exhaust 

Blast 

Blast 

Blast 

Blast 

Exhaust 

Exhaust 

Blast 

Exhaust 

Exhaust 

Exhaust (Intermittently) 

Blast 

Blast 

Exhaust 

Exhaust 

Exhaust 

Exhaust 

Exhaust 

Exhaust 

Blast 

Exhaust 



Exhaust 

Exhaust 

Exhaust 

Exhaust 

Exhaust for two hours 

Exhaust 

Blast 

Exhaust 20-25 minutes 

Exhaust for one hour 

Exhaust >2 to I hour 

Exhaust. 

Exhaust 

Exhaust >4 to I hour 

Exhaust 

Exhaust 

Exhaust 

Exhaust for two hours 

Exhaust "for a while" 

Exhaust 

Exhaust 

Exhaust 

Exhaust 

Exhaust 

Exhaust 

Exhaust 

Exhaust 



VENTILATION 115 

CAPACITY 

There is unfortunately no authoritative rule for determining 
the amount of air needed to renew that vitiated by the respira- 
tion of men and animals working in tunnels. For coal mines 
many States have provided a legal minimum which ranges from 
I GO to 300 cubic feet per minute for each man and from 300 
to 600 cubic feet for each animal. These figures, however, 
have practically no bearing on tunnel work, because in coal mines 
a much larger volume of air than that actually needed by the 
men must be supplied in order to dilute and render harmless the 
inflammable and dangerous gases given off from the coal. In 
many States the laws provide that even these requirements must 
be increased at the discretion of the mine inspector. Condi- 
tions in metal mines, on the other hand, are more closely akin 
to those in tunnels, but, unfortunately, wherever any legislation 
exists at all it merely stipulates that the ventilation must be 
''adequate." 

Robert H. Richards considers that the following air quantities 
are sufficient for proper ventilation in metal mining work : * 

Per light, i cubic foot per minute. 
Per man, 25 cubic feet per minute. 
Per animal, 75 cubic feet per minute. 

The Mining Regulations Committee of the Transvaal, on the 
other hand, provide (for metal mines) a minimum of 70 cubic 
feet per man per minute. t When a person is sitting in repose 
as in a theater or meeting-hall, 20 cubic feet of fresh air per 
minute is considered adequate provision by engineers making a 
specialty of ventilation, but much larger quantities are of course 
required when working. The following table giving the results 
of a test, conducted by Bernhardt Draeger,t shows the amount 
of air breathed in the first minute after performing various 
kinds of work. 

*" Mining Notes." Richards, Robt. H., Vol. II, p. 142. Thos. Todd, 
Boston, 1905. 

\ Eng. and Min. Jour., November 5, 1910, p. 899. 
X Gliickauf, 1904, No. 42. 



116 



MODERN TUNNELING 



QUANTITY OF AIR ACTUALLY BREATHED IN FIRST MINUTE 
AFTER EXERTION 


Kind of Work 


Subject 


Subject 
B 


Subject 
C 


Average 


Sitting 10 minutes 

Walking 270 yards 

Marching 550 yards 

Running 270 yards .... 
Rolling barrel weigh- 
ins: ^A cwt 


8.5 liters 
10.5 " 
143 " 
30. 

38. 

38- :: 
52. 

40 sees. 


8.25 liters 
II. 3 " 
17-5 " 
30. 

^^- ;: 

42. 

61. 

42 sees. 


9 . liters 
II. 7 " 
13.0 " 
30. 

405 " 
38. " 
59- " 

42 sees. 


8 . 58 liters* 

1 1. 2 

14.9 " 
30. 

37-2 " 

39- 

51. 

41 sees. 


Running 550 yards .... 

Race, 270 yards 

Time of race .... 



* I liter = 0.0353 cu. ft. 

These figures give the amount of pure air actually exhaled and 
inhaled, but of course, in order that the products of respiration 
may be diluted sufficiently for the air in the confined space of 
a tunnel to be kept pure, a much larger quantity than this must 
be supplied. Assuming that 20 cubic feet is sufficient for a 
man at rest, and applying the ratio deduced from Draeger's 
table, it would appear that the following volumes of air should 
be supplied for ventilation if the same exercise were undertaken 
in a small room or in a tunnel : 

Ventilation Required When Exercising in a Restricted Space 

Sitting, 20 cubic feet per minute. 
Walking, 26 cubic feet per minute. 
Marching, 35 cubic feet per minute. 
Running, 70-90 cubic feet per minute. 
Rolling barrel, 85 cubic feet per minute. 
Race, 130 cubic feet per minute. 

Although some members of the tunnel crew, such as the shovelers, 
ordinarily work as hard as men running or roUing a barrel, 
the work of the drillers as a rule more closely approximates 
the exertions required in walking; so, taking everything into 
consideration, it would seem that 75 cubic feet per minute 
should be adequate provision for tunnel ventilation, as far as 
the requirements of human respiration are concerned. Assum- 
ing that an animal requires two to three times the air needed 
for a person, on this basis 150 to 200 cubic feet per minute 



VENTILATION 117 

should be furnished each of them. At mine tunnels where any 
attempt is made for even moderate progress, from 8 to 15 men, 
and possibly two animals, are employed in or near the heading. 
Under these conditions 600 to 1,500 cubic feet of fresh air per 
minute would be required for purposes of respiration. It is 
true that some air is furnished by the exhaust from the drills, 
but their action is intermittent and the supply never adequate, 
so that much dependence cannot be placed upon it; on the 
whole, it is much better simply to ignore this possible source 
when deciding upon the capacity of ventilating machinery. 

Although the above capacity is sufficient for ordinary require- 
ments, a much greater, and indeed the maximum, demand for 
ventilation occurs immediately after blasting, when it is obvi- 
ously important to remove the gas and smoke quickly so that 
the men may resume work with the least loss of time. The 
volume to be removed depends largely upon the amount of 
explosive employed; for customary charges under normal con- 
ditions it would probably not vary greatly from 60,000 cubic 
feet, the average result of practical experience at tunnels where 
information bearing on this question was obtainable. It is 
true that ordinarily the air is seldom contaminated by the blast 
for more than 150 feet from the face, which in a heading of 
70 square feet cross-section would have a volume of but 10,500 
cubic feet, and it might appear that the removal of this amount 
of bad air would clear the tunnel. Such might be the case 
provided the smoke could be removed instantly, but this is of 
course not attainable in practice. The readiness with which 
gases become diffused must be taken into consideration, es- 
pecially in this case, since it is customary, immediately after 
blasting, to turn a jet of highly compressed air into the heading. 
Such a practice is necessary because, to avoid injury from 
fl>dng rock, the ventilating pipe rarely extends nearer the breast 
than 100 feet, so to remove the gases they must be forced out 
of the extreme end of the tunnel into the influence of the suction 
of the ventilating pipe. The result is that as a portion of the 
bad air is removed its place is occupied by fresh air, w^hich quickly 
becomes contaminated, and it is necessary, therefore, to remove 



118 



MODERN TUNNELING 



nearly six times the amount of foul air to clear the tunnel. In 
order to be considered good practice, under ordinary conditions 
this should be done in fifteen minutes, requiring an exhauster 
capable of removing 4,000 cubic feet per minute. 

This capacity, however, is necessary for only a few minutes 
after blasting. It is desirable therefore to have the fan or blower 
so arranged that ijt can exhaust for a short time at full load and 
then be run at a lower speed and supply the heading with the 
smaller volume needed for respiration. Such was the case at 
the Laramie-Poudre tunnel, where the exhauster was directly 
connected to a water-wheel and commonly removed approxi- 
mately 1,300 cubic feet running at 100 r. p. m. But immediately 
after blasting the blower was speeded up to 300 r. p. m. when it 
exhausted nearly 3,900 cubic feet per minute, clearing the 
heading usually in 15 to 20 minutes. 

At the Rawley tunnel an attempt was made to secure 
the same result by operating the blower intermittently at 
or near full load. Although the operation of the blower or 
fan at full load for one-third of the time supplies the heading 
with an equal amount of air as when running at one-third 
capacity all the time, different results are obtained in practice. 
The purity of the air is not maintained so nearly constant with 
the intermittent system, and since the starting and stopping 
of the blower are usually dependent upon some man, they are 
apt to be forgotten or neglected. This method of ventilating, 
therefore, cannot be commended. 

PRESSURE 

It is, of course, essential that the required amount of air be 
actually delivered to, or removed from, the heading; to do this, 
pressure is necessary in order to overcome the frictional resist- 
ance to the flow of air in the pipe. This pressure must be 
generated by the fan or blower and may be either positive, 
when forcing air in, or negative, when exhausting it; in either 
case the amount required depends upon the quantity of air 
passed and the size and length of pipe. Although the relations 
between these several factors are somewhat complicated, they 



VENTILATION 



119 



arc shown in the following formula advocated by George S. 
Hicks, Jr.: 



q = 44.72 



14.7^) 



Ig 



Where q 
d 
P 



= quantity of air in cubic feet per minute. 

= diameter of pipe in inches. 

= absolute initial pressure in pounds per square 

inch. 
= length of pipe in feet. 
g = specific gravity of gas referred to air as unity. 
From which we obtain by transposing: 



/ 



P - ^ 216.10 + 



fl 



- 14.7 



2000 d^ 

Where p = P — i^.jjOr the required pressure in pounds pei 
square inch, 
^ = I- 
It must be borne in mind that the formula is theoretical 
and does not take into consideration leakage, the extra friction 
due to elbows in the pipe, etc., but it is said to be based on 
good general practice for air and gas transmission and to give 
fairly satisfactory results. The following table, calculated from 
the formula, shows the pressure, in pounds per square inch, 
required to pass air through various sizes and lengths of pipe, 
assuming its quantity to be 4,000 cubic feet per minute (the value 
derived above as a suitable maximum capacity for a ventilating 
blower or fan). 

Loss OF Pressure, in Pounds per Square Inch, When Forcing 4,000 
Cubic Feet of Air per Minute Through Various Lengths and 
Sizes of Ventilating Pipe 



Diameter 
of pipe, 








Length of Pipe in 


Feet 












in 
inches 


1,000 


2,000 


3,000 


4,000 


5.000 


6,000 


8,000 


10,000 


12.000 


14.000 


6 

8 

10 

12 

14 

16 

18 

20 


20.2 

6.75 
2.52 
1.06 
0.50 
0.26 
0.14 
0.085 


11:8* 
4.69 
2.05 
0.98 
0.51 
0.29 
0.17 


6*65 
2.90 

1-45 
0.76 

0.43 
0.25 


8-45 
3-87 
1 .90 
1.02 
0.58 
0.34 


10. 1 
4.71 
2.32 

125 
0.70 
0.42 


552 
2.77 
1.48 
0.84 
0.50 


7 
3 

I 
I 



06 
60 

95 
II 

67 


8 

4 
2 
I 



63 
40 
40 
38 
83 


9 

5 
2 
I 



87 
16 

84 
64 
99 


590 
3-27 
1.89 

115 



120 



MODERN TUNNELING 



If the pressure cannot be increased to correspond with the 
length of pipe, the volume of air delivered is diminished (the 
size of the pipe remaining the same) . This is illustrated in the 
following table in which a maximum pressure (P — 14.7) of one 
pound per square inch is assumed. 

Maximum Air Capacities in Cubic Feet per Minute of Pipes of 
Different Sizes and Lengths When the Initial Pressure Is One 
Pound per Square Inch 



Diameter 


Length of Pipe in Feet 


of pipe, in 
inches 


1,000 


2,000 


3,000 


4,000 


5.000 


6,000 


8,000 


10,000 


12,000 


14,000 


6 

8 

10 

12 

14 

16 

18 

20 


685 
1410 
2465 
3890 
5720 

7985 
10,720 

13,950 


485 
1000 

1745 
2750 

4045 
5645 
7580 
9865 


'815 
1425 
2245 
3300 
4610 
6190 

8055 


705 
1235 
1945 
2860 
3990 
5360 
6975 


630 
1 105 
1740 
2560 
3570 

4795 
6240 


575 
1005 

1590 
2335 
3260 

4375 
5695 


870 

1375 
2020 
2825 
3790 
4930 


780 
1230 
1810 

2525 
3390 
4410 


710 
1125 
1650 
2305 
3095 
4025 


660 
1040 
1530 
2135 
2865 
3730 



The following table shows the calculated pressure required 
to overcome frictional resistance in passing a volume of air 

Pressure Required to Force Amount of Air Equivalent to Catalogue 
Rating of Ventilating Machine to Proposed Length of Tunnel 
Through Pipe Chosen 



Tunnel 



Carter 

Central 

Laramie-Poudre 

Los Angeles Aqueduct: 

Elizabeth Lake .... 

Little Lake 

Grape- Vine 

Lucania 

Marshall-Russel 

Mission 

Nisqually . ; 

Rawley 

Roosevelt 

Siwatch 

Snake Creek 

Strawberry 

Utah Metals 



Rated 


Diameter 


Stated length 


Pressure 


capacity. 


vent. 


of vent, pipe 


required. 


cu. ft. per 


pipe. 


when tunnel 


in lbs. per 


minute 


inches 


is completed 


sq. in. 


1560 


15 


7600 


0.41 


5540 


19 


9500 


1-93 


3900 


14K 


9200 


3-34 


6350 


18 


13000 


4.14 


2500 


12 


3000* 


1.23 


2500 


12 


1500* 


0.63 


3120 


183^ 


12000 


0.87 


4160 


123^ 


II 000 


8.30 


2500 


10 


13000 


10.25 


2400 


14 


5000 


0.87 


2500 


I2>^ 


6200 


2.02 


4800 


16K 


15700 


4.38 


1560 


ID 


5000 


I 94 


4650 


16 


14000 


4.27 


4000 


14 


19000 


7-50 


4880 


12 


II 800 


1324 



* This division contains a number of tunnels. The distance given is the maximum. 



VENTILATION 121 

equal to the rated capacity of the ventilation machine, through 
pipes of the sizes adopted, to the headings of some of the tunnels 
visited in the field work. 

It will be observed in these examples that the pressures 
needed ordinarily range from i to 5 pounds, 2 pounds being 
roughly the average. At two of the tunnels in this list, in order 
to secure the extra pressure required to furnish sufficient ventila- 
tion, it was necessary to use a ''booster," as it is called; that is, 
to install a second machine some distance within the tunnel 
and by operating both together virtually doubling the pressure 
otherwise attainable. At the ^lission tunnel, the booster was 
situated near the 5,500-foot station. At the Strawberry, 
both machines had been placed in the tunnel at the time of 
examination, the first one at 4,000 feet and the second at 11,000 
feet. Two other tunnels had not penetrated far enough at the 
time visited to require such additional equipment, but doubtless 
extra provision for obtaining pressure will become necessary 
with continued progress. 

SIZE OF PIPE 

The necessity for high pressures (and hence the use of boost- 
ers) may be ob\dated in large measure by the choice of ventilating 
pipe ha\ing diameters of sufficient size. The difiference between 
a 1 2 -inch and an 18-inch pipe often exerts a great influence on 
the ventilation of the heading, but even aside from added cost, 
indiscriminate enlargement is undesirable, every inch of space 
in the average tunnel being jealously required for other purposes. 

By transposing formula (i) we obtain 



^ 



qH 



2000 (P2_ i4.y2) 



which gives the necessary diameter of the pipe in terms of the 
other variables. The following table shows a number of solu- 
tions of this formula (assuming again that ^ = 4,000 cubic feet 
per minute to be passed) and from it may be found the proper 
size of pipe for use with various pressures and distances. 



122 



MODERN TUNNELING 



Diameter of Pipe in Inches, Required in Order to Deliver 4,000 Cubic 
Feet of Air per Minute with Different Initial Pressures and for 
Various Distances 



n 











Length of Pipe in 


Feet 




























1,000 


2,000 


3,000 


4,000 


5,000 


6,000 


8,000 


10,000 


12,000 


14,000 


I oz. 


2I>< 


24K 


















2 " 


i8>^ 


21K 


23 


24K 








.... 


.... 




3 " 


17 


i9>^ 


21H 


22)4 


23^ 


24>^ 










4 " 


I6>4 


i8>^ 


20 


21K 


22X 


23 


24K 








5 " 


I5>^ 


17H 


19K 


20X 


21% 


22 


23^ 


24^ 




.... 


6 " 


15 


17 


i8>^ 


I9K 


20K 


2I>< 


22>^ 


23 K 


24K 




8 " 


14 


16M 


17^ 


i8>^ 


I9X 


20 


21^ 


22 J< 


23 


23^ 


10 " 


13K 


15X 


1634 


17^ 


i8>^ 


I9X 


20;< 


21^ 


22 


22K 


12 " 


12^ 


14^ 


16 


17 


17K 


18K 


i9>^ 


20>^ 


2X4 


21^ 


I lb.. 


I2>4 


14 


15X 


16 


1634 


I7H 


i8>^ 


I9J< 


20 


20K 


iy2 " 


IlM 


13 


14 


I4K 


I5K 


16 


17 


173X 


18K 


19 


2 " 


lOK 


12K 


13K 


14 


I4K 


15 


16 


l63/< 


I7K 


1734 


3 


9'A 


iiK 


12 


12^ 


I3K 


I33/< 


14K 


I5X 


I5K 


I6J< 


4 


9 


lOi^ 


iiM 


12 


I2>^ 


13 


I33/< 


I4>^ 


15 


I5>^ 


5 


83/< 


10 


iok: 


IlK 


11^ 


^2% 


13 


I3>^ 


14 


14^ 


6 


8^ 


qK 


loX 


II 


II>^ 


Il3/< 


I2>^ 


13 


I3K 


14 


8 


7K 


9 


9^ 


lOX 


io>i 


IlK 


11^ 


12X 


12^ 


13K 



COMPARISON OF FANS AND BLOWERS 

Within certain limits, the speed at which fans are operated 
determines the volume of air delivered and the pressure gen- 
erated, but these machines are incapable of producing pressures 
much greater than i^ pounds per square inch, and many of them 
are limited to 8, or even 5, ounces. Therefore, as the frictional 
resistance against which air is to be forced or exhausted becomes 
greater through increasing lengths of pipe, the pressure generated 
in the fan must be increased (by greater speed) to the maximum 
limit at which the fan may be operated, and after that is passed, 
the volume of air dehvered necessarily becomes diminished. The 
blower, on the other hand, is capable of much higher pressures, 
8 pounds per square inch being easily attainable, while with 
some makes 15 pounds is possible, and in tunnel work where 
distances are, as a rule, great, the ability to deliver air against 
high resistance is an important consideration in favor of the 
blower. It operates also at a much lower speed when delivering 
the same volume of air against an equal pressure (i : 10 is con- 



VENTILATION 123 

sidered a fair ratio), and this lessens the wear and tear upon 
belts and machinery. Because of its higher pressure, the blower 
makes it possible to choose a smaller diameter of pipe, a factor 
worthy of consideration, since not only the initial cost, but also 
the space occupied, must be taken into consideration. The first 
cost of the fan, on the other hand, is less than that of the blower, 
and to economize room and obviate the wear on the belt it may 
be connected directly to electric motors, the greater cost of 
low-speed motors tending to prevent this possibility with a blower. 

CONCLUSION 

In most cases a machine of the blower type, capable of high 
pressure, is better adapted for tunnel ventilation where resist- 
ances are apt to be great. For best results the ventilating pipe 
should be so arranged that the direction of the air current may 
be alternated at will, exhausting for a short time after shooting, 
and blowing for the remainder of the time. The blower should 
be adjusted to operate at two capacities: a lower one supplying 
600 to 1,500 cubic feet per minute as determined by the number 
of men and animals, and a higher one capable of exhausting 
approximately 4,000 cubic feet per minute, which would make it 
possible, under ordinary conditions, for the men to resume work 
in the heading about fifteen minutes after shooting. The press- 
ure generated in the blower must be properly adjusted to the 
size of the pipe and the length of the tunnel in order that the 
determined volume of air shall be actually dehvered to or removed 
from the heading. The pipe chosen should be of such size that 
only a moderate pressure at the blower is required, at the same 
time due consideration being accorded such items as cost of 
pipe, and the space such pipe must occupy. 

Turbo-compressors, however, which are especially suited for 
high rotative speeds of electric motors, making it easily possible 
to connect the two directly without loss due to speed reduction, 
which are capable of maintaining a high efficiency (nearly double 
that of the centrifugal fan and fully equal to, if not greater 
than, that of the blower) even after long service, and which may 



124 MODERN TUNNELING 

be designed by using a proper number of stages to deliver air 
against any given resistance, will deserve serious consideration, 
as soon as they are made in suitable sizes, as a possible choice 
for ventilation machiner}' . 



CHAPTER VII 

INCIDENTAL SURFACE EQUIPMENT 

In connection with the blacksmith and repair shops, mention 
should be made of the drill-sharpening machine and the com- 
pressed-air meter. The use of the former is quite common, 
being employed at a majority of the tunnels visited; but the 
latter, so far as could be learned, has been used only in one or 
two places, although there appears to be a field for its employ- 
ment in tunnel plants. 

DRILL-SHARPENING MACHINES 

Several types of drill-sharpening machines are used in the 
United States, each consisting essentially of a frame on which 
two cyhnders are mounted (one vertically, the other horizon- 
tally), each containing a reciprocating piston. Compressed air 
is employed as the motive power, the consumption ranging from 
30 to 100 cubic feet per minute at 85 to 100 pounds pressure, 
according to figures given by the manufacturers. Some device 
is necessary to hold the drill steel firmly in place. The sharp- 
ening is accomplished by means of suitable dies or dolhes, which 
are either attached to or struck by the proper piston and mold 
the hot steel into the desired shape. The piston and die acting 
vertically is used for drawing out the corners of a broken or a 
very dull bit, or swaging out the grooves between the points, or 
insuring that the bit is of the required gauge, while the horizontal 
one sharpens the cutting edges. With a suitable set of dies, the 
machine may be used also for the construction of new bits from 
ordinary drill steel. 

The use of a sharpening machine results in some saving of 
labor cost, for but one operator is required, who need not even 

125 



126 



MODERN TUNNELING 



be high-priced. Such a man can ordinarily turn out several 
times the work of a skilled blacksmith and helper sharpening 
bits by hand. One manufacturer claims that his machine, when 
handled by an expert, is capable of sharpening 250 drills per 
hour, but he states also that half that number, under normal 
conditions, is good work. With another type, the capacity is 
given as 60 to 100 sharpened drills per hour. The lowest of 
these figures is more than ample for the usual requirements of 
tunnel work since, according to figures obtained at tunnels 
visited, the number of drills ordinarily sharpened ranges from 
100 to 200 per day, although in hard ground as many as 400 
were used. 

The labor saved in the blacksmith shop is only a minor 
consideration, however, for the real superiority of the machine 
over hand-sharpening lies in its ability to turn out perfect bits. 
Since the progress in tunnel-driving is often largely determined 
by the time required to drill a round of holes, this important 
part of the work deserves careful attention. It has been demon- 
strated repeatedly by practical experience that on comparing 
the cutting qualities of a machine bit with one sharpened by 
hand there is a marked difference in favor of the former. This 
is due to the fact that the bits come from the machine true to 
gauge, thus greatly reducing the danger of binding or sticking 
in the hole ; there is, therefore, less delay in drilling and a smaller 
loss of time from this cause for the driller and helper (or perhaps 
the entire crew), and there is less likelihood of ''lost" holes. 
Then, too, the bits being correctly shaped and properly sharp- 
ened, they not only ''stand up" better and stay sharp longer, 
but they also drill faster, and it is not necessary for the drill 
crew to change steel so often, thus reducing another source of 
delay. The use of drill-sharpening machines at the ordinary 
tunnel plant is, therefore, strongly recommended not only for 
its saving of time and labor both in the blacksmith shop and 
in the heading, but also for its abihty to make bits whose superior 
drilling quahties will easily pay, because of additional pro- 
gress, a handsome return upon the money invested in the 
machine. 



INCroENTAL SURFACE EQUIPMENT 127 

AIR METERS 

Air meters are of various types, depending upon differences 
in principle and design. In one of them the volume of air is 
measured by causing it to impinge consecutively upon a number 
of turbine wheels mounted on a common shaft which is con- 
nected with a registering device by a properly designed master 
gear. The machine is calibrated to read in cubic feet per 
minute of free air and is claimed by the manufacturer to give 
accurate measurements of air under varying pressures. A 
second type operates upon the principle that, with a uniform 
difference of pressure on both sides of an orifice and a constant 
initial pressure and temperature, the quantity of air passed 
is proportional to the size of the orifice. In this machine the 
difference in pressure on the two sides of the diaphragm is 
kept uniform by the constant weight of a taper plug which 
closes the orifice until the difference in pressure is sufficient 
to raise the plug and support it. The taper is so designed that 
the amount of air passed through the orifice is directly propor- 
tional to the rise of the valve, and this movement is multipHed 
and transmitted to a needle which records it upon a moving 
sheet of paper, thus affording a means of measuring the volume 
of air passed. A third type consists in a device for determining 
the pressure due to the velocity of the flow of air in a pipe (which 
is proportional to the amount of air passed if the temperature 
and initial pressure are constant) and transmitting that pressure 
to one arm of a U-tube filled with mercury. The tube is bal- 
anced on knife-edges, and since the pressure causes a flow of 
mercury to the other arm, the balance is disturbed and the 
tube is deflected, the amount of deflection being commensu- 
rable with the flow of air. This is transmitted by levers 
to a recording needle. In a fourth type, although only a 
proportional volume ranging from % oi i per cent, to 8 per 
cent, is actually measured, the recording device registers in 
terms of the fuU loo per cent, volume. 

Any of these meters may be used to determine the amount 
of compressed air delivered to a purchaser. Their most im- 



128 MODERN TUNNELING 

portant use, as far as tunnel work is concerned, is in determining 
the amount of air used by rock drills. It is well known that all 
pneumatic rock drills show an increased air consumption (which 
is less in some than in others, to be sure, but appreciable in all) 
caused by leakage, etc., as the various parts become worn 
through use. This fact is quickly discovered in practice and 
a large number of actual tests bear out the statement that after 
six months' or a year's steady use of the ordinary rock drill, 
the amount of this loss will range from 20 to 40 per cent. This 
additional air is not only expensive to compress, but, what is of 
more importance, the efhciency of the drilHng machine is lowered 
at the same time, and the man behind it is unable to do as 
much effective work, thus entailing further loss. If the drill 
repair man has to guess at the air consumption, it is very diffi- 
cult for him, even though he is an expert mechanic, to send a 
drill from the repair shop back to the heading that will do as 
good work as when it was new. But if the shop is provided 
with some means of determining the air required by the drill, 
he is much better able to remedy the defects and make the 
proper repairs. This results in a saving of expensive power 
and increases the efficiency of the drill and the amount of work 
done by the driller. It is very desirable also to keep a record 
every time the drill leaves the repair shop, not only of the cost 
of repairs, but also of its present air consumption, in order that 
upon its next return a comparison may be made with the last 
record, as well as with the nominal air requirements. By such 
a course necessary repairs may be made, if the air consumption is 
excessive, that would perhaps have been unsuspected otherwise, 
while at the same time the manager may keep an accurate 
statement of drill repairs and inefficient drills may be weeded 
out. The following sample gives a rough outline of such a 
system :* 

DRILL RECORD 

Tool Piston drill Maker Size 2/4 inches 

Purchased 2/1 /lo Serial No. 123,456 Shop No. 12 

Normal air consumption, 90 cu. ft. per min. at 75-80 lbs. 

* By courtesy of the Kxeelsior I- rill and Mfg. Co. 



INCIDENTAL SURFACE EQUIPMENT 



129 



Date 


Air Consumption 


Pressure 


Repairs 


2/24/10 


94 


76 


2 side rods 


3/10/10 


99 


78 


2 pawl springs 
I leather cup 
I chuck bolt 
I chuck key 


5/10/10 


128* 


75 


I air chest and valve* 


back to 


96 




2 piston rings 



* Excessive air consumption corrected by repairs indicated. 



CHAPTER VIII 

ROCK-DRILLING MACHINES 

TYPES 

As a rule, rock-drilling machines are classified primarily 
according to the motive power by which they are operated. 
The great majority of those used in tunnels are of the pneumatic 
type, but hydraulic and electric drills have been employed. For 
surface work, steam is sometimes substituted for compressed air 
by making a few minor alterations in pneumatic drills, and 
machines using gasoline power are also to be found on the 
market; but the difhculty with the former in disposing of ex- 
haust steam and with the latter the products of combustion, 
prevent any extensive use of these types underground. The 
following paragraphs describe some of the principal features of 
the various rock drills employed in tunnel work. 

Pneumatic Drills 

The pneumatic rock drill consists essentially of a cylinder 
containing a piston or a hammer which is reciprocated by the 
proper admission, application, and release of compressed air. 
In the piston type of air drill, a drill steel provided with cutting 
edges is alternately made to strike and recede from the rock by 
the movement of the piston to which the steel is firmly attached. 
In the hammer drill, the steel does not reciprocate, but is held 
loosely against the rock to which it merely transmits blows 
received from a moving hammer. (See Figure 28.) Piston 
drills are, almost without exception, mounted in a shell or cradle 
which may be attached to some rigid support while the drill is in 
operation, but which is easily removed when necessary; a screw 
thread is provided also, permitting the drill to be fed forward 
in the shell as the hole grows deeper. In some types of hammer 

130 



ROCK-DRILLING MACHINES 



131 



drills, especially those used 
for sloping and trimming, 
the shell is omitted and 
the drill either is held in 
the hand or is provided 
with a telescoping feed, 
operated automatically by 
compressed air. In either 
type, some device is re- 
quired to rotate the drill 
steel in order that the cut- 
ting edges of the bit may 
not strike repeatedly in 
exactly the same place. In 
cradle-mounted drills this 
is generally accomplished 
by a mechanism (consisting 
of rifie-bar, ratchet, and 
pawls) which is arranged 
to turn the piston or ham- 
mer, this in turn rotating 
the chuck holding the drill. 
Where the telescoping feed 
is employed it is necessary 
to rotate the entire machine 
by hand. Figure 29 shows 
a section through a piston 
pneumatic rock drill and 
gives a Hst of the princi- 
pal parts. 

Pneumatic drills are 
often differentiated by the 
method employed in con- 
troUing the admission of 
air to the cyHnders. This 
may be accom_plished by 

tappet, air-thrown, or aux- Fig- 28. Section through a hammer dril 



132 



MODERN TUNNELING 



iliary valves, or the air supply may be regulated directly by the 
movement of the piston or hammer itself. 

The action of the tappet valve is illustrated in Figure 30, 
which shows a section through a drill equipped with the same. 
As the piston in operation moves from the position shown in 




Fig. 29. Section through a piston rock drill. 

I, Cylinder; 2, Air chest; 3, Inlet port; 4, Exhaust port; 5, Reverse 
ports; 6, Valve; 7, Valve bushing; 8, Buffer; 9, Check nut; 10, Top head; 
II, Oil chamber; 12, Ratchet ring; 13, Rifle bar; 14, Ratchet; 15, Plug; 
16, Feed nut; 17, Lock washer; 18, Check nut; 19, Washer; 20, Feed 
handle; 21, Yoke; 22, Feed screw; 23, Shell; 24, Trunnion; 25, Lower head; 
26, Clamp bolt; 27, Bushing; 28, Gland; 29, Packing; 30, Piston; 31, Clamp 
bolt; 32, Chuck bushing; 33, Chuck button; 34, Piston rings; 35, Cylinder 
ports. 

the cut tovv^ard the lower end of the cylinder, the crank end of 
the tappet rises, while the other end drops into the depression 
of the piston, thus producing a sHght rotation around the tappet 
pin, which is sufficient to move the sHde valve. This admits 
live air against the lower end of the piston, at the same time 
connecting the upper end of the cylinder with the exhaust pipe. 
The piston, therefore, starts in the other direction, and a similar, 
but reverse, process takes place. 

The operation of the air-thrown valve is somewhat more 
compKcated than the tappet, but by referring to Figure 29, 
which shows a section of a drill equipped with the usual 
form of air-thrown valve, the action is shown to be as follows: 
The piston is indicated as just starting on the down stroke, the 
valve being so placed that live air is entering the top cylinder 
port (35) from the air inlet port (3) by way of the connecting 
passages indicated by dotted lines, while at the same time the 



ROCK-DRILLING MACHINES 



133 



front of the cylinder is connected with the exhaust (4) by the 
lower cylinder-port and its air-ways. The upper end of the 
''spool'' of the valve 
is connected with the 
lower end of the 
cylinder — and hence 
with the exhaust — 
by the reverse port 
(5) (shown unshaded 
in the illustration). 
As soon as the piston 
in its travel uncovers 
the other reverse 
port (5) (shown by 
dotted lines), pres- 
sure from the upper 
end of the cylinder 
will be transmitted 
to the lower end of 
the spool and throw 
it against the upper 
end of the valve chest, 
and this will alternate 
the connection of the 
ports for live air and 
exhaust, thus revers- 
ing the piston. A 
similar process is then 
repeated on the up- 
stroke. 

In a recent modi- 
fication of the usual 
air-thrown valve the 
spool is replaced by 
a cyHndrical shaft 
carrying two flat 
wings, which some- 




FiG. 30. Section of a tappet valve drill. 



134 



MODERN TUNNELING 



what resemble those of a butterfly. The operation of this 
valve is illustrated somewhat diagrammatically in Figures 31, 
32, and 2)2)' In Figure 31 the piston P is represented as about 



Supply 




Fig. 31. 



S-Supply 



SS2 




Fig. 32. 



S -Supply 




Fig. 33. 
Figs. 31, 32, and 33. Action of butterfly valve. 

to Start on the forward stroke. The valve is thrown so that live 
air is permitted to enter through the supply ports S, S2, and SS2, 
while the spent air in the front end of the cylinder is exhausting 
through the ports ^E^i, Ei, and the exhaust E. As soon as the 
piston in its forward movement uncovers the exhaust port EE2, 
live air will pass through EE2 to E2, and its pressure on the 
valve at this point will balance its pressure on the opposite wing 



ROCK-DRILLING MACHINES 



of the valve facing 
port 52. The valve 
will then be in equihb- 
rium, but will be held 
stationary with the 
ports 5*2 and Ei open 
because of the hnpact 
of the air opposite S2. 
Near the end of the 
stroke, however, the 
piston closes the ex- 
haust port EEi, and 
in passing from EEi 
to Fi it compresses 
the air which is trap- 
ped in the clearance 
space at the end of 
the cyhnder. This 
cushion pressure, 
communicated 
through the cylinder 
ports SSi to Si, is 
sufhcient to throw the 
balanced valve to the 
position shown in 
Figure 33. Live air 
is then admitted, 
through Si and 6*51, 
the exhaust ports ££2 
are opened, and the 
piston starts on the 
return stroke. 

One form of aux- 
iliary valve used on 
a well-known piston 
drill is described as a 
mechanism in which 




Fig. 34. Section through a tappet auxiliary 
valve drill. 



136 



MODERN TUNNELING 



the strains, shocks, and jars to which the tappet or rocker is 
subjected are transferred from the main valve, with its vital and 
d6licate functions, to a smaller auxiliary valve weighing only a 
few ounces, especially designed to withstand the service. This 
drill is illustrated in Figure 34. 

When the drill is in operation, one end or other of the auxiliary 
valve projects slightly into the cyHnder, and is thrown by the 
piston in its travel. The movement is perfectly free and very 
short — only enough to uncover a small port and release pressure 
from one end of the main valve, which is at once thrown by 
the resulting unbalanced pressure, opening wide the main port 
and admitting compressed air to the other end of the piston for 




Fig. 35. Section through a steel-ball auxiliary valve. 

the return stroke. The auxiliary valve is simply "sl trigger which 
releases the main valve." 

In another form of auxiliary valve, the main air-thrown 
spool is controlled by two auxiliary valves consisting of steel 
balls which are positively actuated by the movements of the 
piston. See Figure 35. In this figure the piston A is repre- 
sented as having just started on the down stroke. Compressed 
air is entering the upper end of the cylinder through the port G 
and the spent air in the lower end is escaping through the port H 
and the exhaust chamber /. At the end of the stroke the ball C 
will drop on its seat and the ball D will be raised, thus allowing 
the air in the end of the valve chest at F to exhaust past D 
through the port between the upper and lower balls. The un- 



ROCK-DRILLING MACHINES 



137 



balanced pressure thus produced throws the valve to the other 
end of the chest, which reverses the connections between the 
cylinder chambers and the inlet and exhaust ports. The piston 
therefore starts on the return stroke and a similar but reverse 
process takes place. 

The valveiess air-regulating mechanism, in which the move- 
ment of the piston itself covers and uncovers various ports, is 
employed almost exclusively on drills used for stoping only. 
Although rarely chosen for tunnel work, a brief description of 
this method of regulating air supply is warranted by its extensive 




Fig. 37. 
Figs. 36 and 37. Cross-sections through valveiess drill. 

use in its own field. The principle of operation is illustrated in 
Figures 36 and 37, which are two cross-sections through the 
cylinder of one make of valveiess drill. In Figure 36, air under 
pressure enters from the feed cyhnder through the port a and 
passes to the front of the piston, where it exerts pressure at all 
times. The piston is forced back until the port e (Figure 37) is 
uncovered, when compressed air passes through the port / and 
exerts pressure on the top of the piston. Since the area of this 
face is greater than the striking end, the piston starts forward. 
Live air is shut off when the port e is closed, but the piston is 
pressed forward by the expansion of the air until the exhaust 
port h is opened just as the blow is struck on the drill steel. 



138 



MODERN TUNNELING 



Hydraulic Drills 

The best known hydraulic rock drill is, perhaps, one of the 
rotary type developed for use in the Simplon tunnel, which 
consisted essentially of a hollow steel tube armed with teeth 
which were held firmly against the rock by hydraulic pressure 
while at the same time the tube was slowly revolved by a water- 
driven motor. Although, as far as could be ascertained, it has 




SECTION' A-A 



1-1- 










Scale 






Inches 12 

1 


9 





3 







1 


2 Feet 
1 













0.5 




1M« 



Fig. 38. Rotary hydraulic rock drill. 



never been used for tunnel work in the United States, the intro- 
duction of the following description (see Figure 2>^), as given by 
Prelini,* we consider warranted by its historically interesting 
foreign achievements: 

''This rotary motion is given by a twin-cylinder single-acting 
hydraulic motor (e), the two pistons, of 2^ inches stroke, acting re- 

* "Tunneling," page 103. 



ROCK-DRILLING MACHINES 139 

ciprocally as valves. The cranks are fixed at an angle of 90° to 
each 'Other on the shaft, which carries a worm-gearing with a worm- 
wheel iq), mounted upon the shell (r) of the hollow ram {i), and 
this shell in turn engages the ram by a long feather, lea\ing it free 
to slide axially to or from the face of the rock. The average speed 
of the motor is 150 revolutions to 200 revolutions per minute, the 
maximum speed being 300 revolutions per minute. . . . The press- 
ure on the drill is exerted by a cyhnder and hollow ram (z), which 
revolves about the differential piston (5), which is fixed to the envel- 
ope holding the shell (r). This envelope is rigidly connected to the 
bedplate of the motor, and, by means of the vertical hinge and pin 
(/), is held by the clamp (T^ embracing the rack-bar. When water 
is admitted to the space in front of the differential piston the ram 
carrying the drilling-tool is thrust forward, and when admitted to the 
annular space behind the piston, the ram recedes, withdrawing the 
tool from the blast-hole. The drill proper is a hollow tube of tough 
steel 2^ inches in external diameter, armed with three or four sharp 
and hardened teeth, and makes from five to ten revolutions per minute, 
according to the nature of the rock. When the ram has reached the 
end of its stroke of 2 feet lyi inches, the tool is quickly withdrawn 
from the hole and unscrew^ed from the ram; an extension rod is then 
screwed into the tool and into the ram, and the boring is continued, 
additional lengths being added as the tool grinds forward; each 
change of tool or rod takes about 15 seconds to 25 seconds to perform. 
The extension rods are forged steel tubes, fitted with four-threaded 
screws, and having the same external diameter as the drill. They 
are made in standard lengths of 2 feet 8 inches, i foot 10 inches, and 
11^ inches. The total weight of the drilling-machine is 264 pounds, 
and that of the rack-bar when full of water is 308 pounds. The ex- 
haust water from the two motor cylinders escapes through a tube 
in the center of the ram and along the bore of the extension rods and 
drill, thereby scouring away the debris and keeping the drill cool; 
any superfluous water finds an exit through a hose below the motors, 
and thence aw^ay dow^n the heading. The distributor, already men- 
tioned, supplies each boring-machine and the rack-bar with hydraulic 
pressure from the mains, with w^hich connection is effected by means 
of flexible or articulated pipe connections, allowing freedom in all 
directions. The area of the piston for advancing the tool is i5>^ 
square inches, which under a pressure of 1,470 pounds per square inch 
gives a pressure of over 10 tons on the tool, w^hile for withdrawing the 
tool 2^ tons is available." 

A recently invented percussion hydraulic drill is described 



140 



MODERN TUNNELING 



fully in the Engineer,^ from which Figures 39 and 40 and the fol- 
lowing brief abstract are taken: 

The drill consists essentially of a cylinder, in which is a piston C, 
free to move, while at the other end of the cyhnder is a flap valve 
D, which is kept open by a spring. The interior of the cylinder is in 

Bolts for attacliing. 
to drill post 




Fig. 39. Hydraulic percussion rock drill. 

communication with a "striking tube" F G, at the end F of which 
is an air vessel. When the valve H is opened, water flows through the 
apparatus, out past the valve D, into the waste pipe E. The rush 
of water past the valves causes the pressure on the under side to be 
less than the pressure on the upper side, where the velocity is less. . . . 
. . . When the velocity attains a certain value the difference of 
pressure is sufficient to close the valve, and the column of water in 



Air^essel 
A 



Striking Tube 




rpom.Mains p 

Fig. 40. Section through striking tube, hydraulic percussion rock drill. 

the striking tube is suddenly stopped. The kinetic energy of the 
water in the tube is communicated to the piston C, which is impelled 
forward with high velocity, and the drill which is at the end of it 
strikes a heavy blow on the stone or rock being bored. 

The pressure in the interior of the cylinder is diminished by the 
moving out of the piston C, . . . enough for the valve to open. 
Water then streams through the open valve. The piston is meanwhile 
being brought back to its original position by springs, but before 

* " New Hydraulic Rock-boring Y)t\\\" t\iQ Engineer (London), January 
7, 1910, page 24; 2}4 cols, illustration. 



ROCK-DRILLING MACHINES 141 

it is right back . . . the valve D closes, and the direction of motion 
is reversed by the hydraulic shock. The drill then strikes another 
blow as before. The actual apparatus is shown in section and plan 
in Figure 39, which is roughly to scale, the overall length being 
about 4 feet. 

The actual magnitude of the blow depends primarily upon (i) the 
weight of the striking column; (2) the velocity of the water when the 
valve closes; and (3) the weight of the chisel and boring bar. 

The velocity of the column is fixed by the velocity at the valve 
required to produce the necessary difference of pressure to close the 
valve, i.e., it is fixed by the stiffness of the spring controlling the 
valve. The rapidity of the blows is Hmited by the fact that after 
each blow the striking column is brought to rest, and it must be accel- 
erated to the requisite velocity before the valve will close. The 
rapidity of w^orking depends, therefore, upon the pressure which is 
urging the column forward, i.e., it depends on the pressure in the 
supply mains. The actual magnitude of the blow is said to be un- 
affected by the varying pressure in the mains, and to depend only 
on the weight of the striking column and the strength of the spring 
controUing the valve. The inventor claims that machines of the 
type described strike from twenty to thirty blows per second, while 
the maximum speed of percussion machines of existing t}q3es is from 
three to five strokes per second. 

One of these machines has recently undergone a series of tests 
at the Millbank Pumping Station of the London Hydraulic Power 
Company. The pressure used was 450 pounds per square inch. . . . 
The tests were carried out on a block of hard Portland stone. The 
diameter of the drill used was 2 H inches, and on an average progress 
was made in the stone at the rate of 10^ inches per minute. This 
is equivalent to the removal of 46 cubic inches of stone per minute. 
The drills stood up to the work so well that after holes aggregating 
about 25 feet in depth had been drilled, it was not necessary to do 
anything to the edge. A stream of water plays on the chisel the whole 
time, and serves the threefold purpose of keeping the chisel cool, 
of rinsing the bore-hole, and of allaying the dust. 

Electric Drills 

An electric rock drill consists primarily of an electric motor 
and a means of applying the power developed in it to the work 
of drilling rock. In some machines the motor is mounted directly 
upon the drill frame, but in others it is removed a short distance 
and connected to the drill by a flexible shaft, or some similar 



142 MODERN TUNNELING 

device for transmitting power. Provision must also be made 
for preventing the shocks and jars developed by the impact of 
the drill steel upon the rock from being transmitted back to the 
motor, which is a machine incapable of operating for any length 
of time under such conditions. In many of the earlier models, 
springs or cushions of some elastic material such as rubber were 
used for this purpose. These devices failed to give satisfaction 
either because of inability to do the work required or because 
of excessive wear, breakage, and annoyance. In two or three of 
the early models, an ingenious attempt was made to avoid these 
troubles by taking advantage of the fact that if an electric cur- 
rent is passed through a spiral coil of wire, a suitably placed bar 
of soft iron will be drawn into it. By providing two such coils 
or solenoids and causing the current to flow through them 
alternately, an iron piston carrying a drill steel was made to 
reciprocate between them. In order to have the blow sufficiently 
smashing to be effective, however, a prohibitive weight of copper 
wire was needed for the solenoids. To-day practically all elec- 
tric drills use compressed air in some manner to cushion the reac- 
tion of the blow, — a medium possessing the very desirable 
characteristic of extreme elasticity and at the same time not 
affected by wear and tear. In one machine, however, a hammer 
is made to strike the end of the drill steel by centrifugal force, 
the rebound giving the necessary flexibihty. 

One of the successful electrically driven rock drills that has 
been on the market for over five years is illustrated in Figure 41. 
In this machine the drill piston is reciprocated by alternating 
pulsations of compressed air, created by a double-cylinder air 
compressor driven by a standard electric motor. Two short 
lengths of hose connect the air compressor to the drill, each 
running from one of the compressor cylinders to opposite ends 
of the drill cylinder. The air in the system, which acts as an 
unwearing cushion between the pulsator and the drill, is never 
exhausted, but is simply used over and over. The drill is very 
simple — merely a cylinder containing a piston and rotating 
device — and valves, chest, side rods, buffers, and springs are 
omitted, while the compressor has neither valves nor water 



ROCK-DRILLING MACHINES 



143 



jackets. The motor may be designed for either direct or alter- 
nating current as desired, and it is mounted with the compressor 
on a wheeled truck for easy handling. 

A second air-cushioned electric drill of the piston type, but 




Fig. 41. Electrically driven rock drill, shown partly in section. 

one in which the motor is mounted directly on the drill frame, is 
illustrated in Figure 42. In this drill the motor M, which can be 
readily detached from the rest of the machine whenever it is 




Fig. 42. Section through an air-cushioned piston electric drill. 

necessary to move the drill to a new set-up, etc., is connected 
by reducing gears to a crank shaft 5, which drives a connecting 
rod R. This is attached and gives a reciprocating motion to a 
cylinder C, which slides in suitable guides and contains a piston 



144 MODERN TUNNELING 

P, provided with a chuck for holding a drill steel. As the cylinder 
moves forward, air is compressed in the chamber B behind the 
piston and makes the piston move forward, which causes the 
drill bit to strike the rock. During the return stroke of the 
cylinder, the compression of air in the other chamber F brings 
the piston back again with it. Rotation is secured by means of a 
standard spiral nut and ratchet. Details of the feed screw, the 
carriage, and other features are shown in the illustration. 

In an electrically driven air-cushioned rock drill of the 
hammer type (Figure 43), power is transmitted by suitable gears 
and cranks from the motor to a piston and causes it to recipro- 
cate in an air cylinder. The same cylinder contains at its other 
end a hammer, which, however, is in no manner directly connected 
with the. piston. As the latter starts on the down stroke it 
compresses the air in the space between it and the hammer, 
which is projected forward until it strikes the end of the drill 
steel. Just as it does so it releases the compressed air by un- 
covering an exhaust port controlled by a poppet valve. When 
the piston starts on the return stroke the exhaust valve closes 
and a partial vacuum is created which pulls the hammer toward 
the piston. The latter in its travel uncovers an inlet port, also 
poppet controlled, admitting new air, which destroys the vacuum. 
The momentum of the hammer would cause it to strike the piston, 
which again starts on the down stroke were it not for the compres- 
sion of this air entrapped by the closing of the poppet valve as 
soon as the vacuum is destroyed. The drill steel is rotated by the 
motor through a shaft, gearing, and a ratchet. Hollow steel is 
used through which water is forced to the cutting edge by a 
small pump supplied with the drill; but if water under pressure 
is already available, however, the pump may be disconnected. 
Another feature of this drill is the automatic chuck which is 
adapted for using steel as it comes in the bar, thus obviating 
the necessity of forging shanks. 

A fourth electric drill, also having an air-cushioned hammer, 
is illustrated in Figure 44. In this drill as the yoke A moves 
forward, the piston B compresses the air in the chamber C, 
forcing the cylindrical hammer D against the anvil block E, 




u 



146 



MODERN TUNNELING 



which transmits the blow to the drill steel at F. On the return 
stroke of the piston, the compression of air in the chamber G 
brings the hammer back in readiness for another blow. Hollow 




Fig. 44. Sectional view of an electrically operated air-cushioned hammer 

drill. 

steel is employed through which water is forced by a small 
pump whose plunger reciprocates with the drill piston. 

So far as could be learned, the only electric drill in service 
to-day which does not use an air cushion is the one illustrated 




Fig. 45. Electric revolving hammer drill with motor and part of casing 

removed. 

in Figure 45. In the illustration will be seen the two hammers 
which, although free to sHde in their sockets in the revolving 
disk, are thrown out by centrifugal force and strike the anvil 



ROCK-DRILLING MACHINES 147 

block, which transmits the blows to the drill steel. The steel, 
which is held in a chuck rotated by a worm gear as indicated, is 
of the auger type, the spirals acting in the capacity of conveyor 
for removing broken rock from the hole. 

Gasoline Drills 

Since the difficulty of disposing of the waste products of com- 
bustion, which are not only hot and disagreeable but also 
contain gases injurious to the health of the workmen, makes the 
gasoHne drill hardly suitable for service underground, and since 
as far as could be learned they have never been used in tunnel 
work, their design and construction will not be discussed here. 
A description of one of these machines having two explosion 
cylinders may be found, however, in the Engineering and Mining 
Journal for November 21, 1908, page 1,008; in the Engineering 
News for November 26, 1908, page 575, and in the Mining and 
Scientific Press for December 19, 1908, page 852. Another drill, 
one of English manufacture, in which a cam, driven by a gasoline 
engine, trips a spring-actuated piston, was described in the 
Engineer (London) for September 36, 19 10, and in the Engineer- 
ing News for November 17, 19 10, page 538. 

MERITS OF EACH TYPE 
Pneumatic Drills 

The chief advantage of the pneumatic rock drill is its ability 
to withstand rough usage and still perform efficient service. 
The work of a rock drill is done necessarily under conditions that 
would quickly destroy almost any other type of machinery. 
It is subjected to constant and severe vibration when in oper- 
ation, for although it is usually held firmly and securely, still 
it cannot be mounted rigidly. Lubrication, when supplied at 
all, is often administered in large doses most irregularly, and it 
is impossible to prevent sand and grit from getting into the 
machine, thus adding greatly to the wear and tear. In many 
cases, men who operate it have no conception of its construction, 
and ignorantly subject it to shocks and strains for which it was 



148 MODERN TUNNELING 

never designed, their first impulse when things go wrong being 
to seize a sledge-hammer and hit the machine in the most con- 
venient place. All drill runners, of course, do not belong to this 
type, but the description fits a much too large percentage of them. 
Everything considered, the rock drill must be capable of being 
operated under the most adverse conditions. This necessitates 
the elimination of all unsuccessful details, the rejection of com- 
pHcated parts that are not absolutely essential, the determination 
of the proper size and strength of those remaining, and the 
selection of materials having the proper stability and wearing 
qualities. This can be accomplished in any machine only after 
patient development and experiment, and it is but natural that 
the pneumatic drill, which has been undergoing such a process 
for more than fifty years, should be able better to cope with 
these conditions and to operate more steadily with fewer inter- 
ruptions and a lower cost for repairing broken or worn parts 
than any of the newer types. 

Among other advantages of the pneumatic drill may be 
mentioned the facts that it furnishes a certain amount of venti- 
lation, that it does away with the introduction underground of 
electricity at comparatively high voltages (which is oftentimes 
a source of danger), and that it does not require pipes strong 
enough to withstand the pressures needed for the rotary 
hydrauHc drill. The air drill, however, should not be relied 
upon for ventilation, because, in the first place, the supply 
of air is intermittent, being arrested while the drill is stopped 
for the purpose of changing steel or moving it into position for 
a new hole, etc. ; in the second place, the drills are not in oper- 
ation immediately after the blast — the time when ventilation 
is most needed— although it is true that the use of pneumatic 
drills makes it possible to direct a jet of compressed air into 
the heading at this time to assist in removing the smoke; and, 
finally, there are on record cases in which the exhaust from 
the drills not only did not deHver fresh air but even filled the 
heading with carbon dioxide and other dangerous gases produced 
by combustion of oil and grease in the receiver, resulting, in 
one instance at least, fatally for several men. Again, at tunnels 



ROCK-DRILLING MACHINES 149 

using electric haulage the adoption of electric drills would 
simply add a Httle to a danger already present rather than intro- 
duce a new one, and in such cases the advantage of the air drill 
in this respect is not so important. 

The most important disadvantage of the pneumatic drill, 
on the other hand, is its well-known lack of power economy. 
Since, as stated by E. A. Rix,* 'Hhe tables set forth in the 
trades catalogues for the consumption of standard piston rock 
drills are fairly accurate," let us determine from them the 
powTr required for rock drills by using his estimate of 20 b. h. p. 
per 100 cubic feet of free air per minute. The lowest figure 
given for any type of rock drill used at the tunnels examined 
for this report is 65 cubic feet per minute at 100 pounds press- 
ure, while drills using as much as 150 and even 175 cubic feet 
wxre very numerous. On this basis, then, without making 
allowance for loss of power through friction in the pipes or leak- 
age in the machines when they become worn, pneumatic drills 
require the application of from 13 to 35 brake horse-power at 
the compressor during the time the machine is operating. Al- 
though the rotary hydrauHc drill employed in the Simplon 
tunnel required as much as 13 horse-power f (exactly the min- 
imum figure just deduced for air drills) it is by comparing the 
power used in air drills wdth even the maximum of 6 horse-power 
for electric drills, many of which run on less than 2, however, 
that the large dift'erence in power consumption is revealed. 

Comparing the different t\^es of pneumatic drills used in 
tunneling, the piston machine has somewhat the advantage 
over the hammer type as regards reliabihty and as regards effi- 
ciency in drilling holes vertically or nearly vertically dow^nward. 
This rehabiHty may be attributed without doubt to its simpler 
construction. It does not contain any mechanism for intro- 
ducing a w^ater spray through a hollow drill steel, it is not 
troubled by crystallization of metal parts from the repeated 

* Address before the Alining Association, University of California, Feb- 
ruary 19, 1908. 

t Comstock, Chas. W. : "Great Tunnels of the World." Proc. Colo. 
Sci. Society., Vol. VIII., p. 363. 



150 MODERN TUNNELING 

shocks of rapid blows, and it has a much greater range of feed. 
This last item is a feature of importance when the machine is 
handled by an inexperienced operator, giving as it does greater 
latitude before the piston begins to strike the front head. These 
considerations make the piston drill more nearly fool-proof, 
and hence better adapted to use by ordinary drill runners — 
especially those in the Eastern States, who, as a rule, are neither 
as intelHgent nor as careful as those in the West. Complexity 
of construction should not be confused, however, with the num- 
ber of parts; for if this were taken as the standard, and every 
screw, bolt, or nut counted separately, it could be shown that 
the hammer drill is the simpler machine. 

The greater efficiency in drilling holes which point downward 
was clearly brought out in the recent extensive drill competition 
in the Transvaal, according to the committee conducting the 
test, who reported that one of the main reasons for the better 
showing made by the piston drills underground was the fact 
that practically all of the holes drilled there were pointed down- 
ward. This is substantiated in several instances at tunnels 
in this country in which the excavation is accomplished by the 
heading and bench method; in such cases the piston drill is 
reported to have given better satisfaction in drilling the vertical 
holes required for the removal of the bench. 

The principal advantages of the hammer drill, of the type 
used in tunneling, are a somewhat lower air consumption and a 
greater speed in drilling holes that are horizontal or nearly so, 
and especially those pointing slightly upward, such as are 
necessary under the ordinary methods in driving tunnel headings. 
In hammer drills the air consumption, and hence the amount of 
power required, varies from 65 to 100 cubic feet per minute at 
100 pounds pressure (catalogue rating at sea level) as compared 
with 125 to 175 cubic feet for piston drills. The rate of drilling is 
of course largely dependent upon the character of rock penetrated, 
but by observation of the table below (in which it will be seen 
that piston drills, even in shale and sandstone, rarely drilled 
over 10 feet per hour, while the hammer drills in granite and 
other hard rock rarely fell below that figure, 15 and even 20 feet 



ROCK-DRILLING MACHINES 



151 



E .S- 



a 
a 
< 



c 
. .2 

> " 
**- o 



rt 



o o 
a; a 



2" - 



rO 



2 E 2 

> w > 





"O 






rt 


g 


«3 


■M 


J3 


>, 








a> 






o 


oj 


-o 






D 


OS 


u - 


JS 


O +j 




rt <u 


jr 


<u 


o 


r^'« 


3 


-*- r^ 


P 


o • 




OS 




<U KH 




M 




2ii 


f,TJ 


O G 


>j= 


C^ o 


< ■'^ 



"Sy 










W S u 


ji <^ 


00 O O C< O 'O lO 


-t O fO o 


o o 


ui " 


1 1 1 


00 « >- ri 
1 


fO ^ 


IR^ 




00 00 c» 


lO o 





OO OC CjiOOOrO 

MM 1-1 O) MHH_HHhH0O 



00 lO 00 O 00 lO vO 



«s ?^ 



a 



c 
-u o 



"rtld g rt g _ 



8*S 

O 03 



!5 2 2 2^ - S 



-M -M CJ -M 



O 



o o 



2^ 



2 2.2 c ^ 3 



S ccEccES 
p oopoopp 



a cj a 







c £ 




c £ 


<U 

£ £ c c c c 


£ £ £ e £ 


g 


g 


.H £ 


£ £ 2 2 2 2 


rt rt rS 03 03 


03 


^ d 


tfi 03 


(^ d (fi vi ui tn 


En:Ka:E 


E 


El 


Ee 


xx'^'^'Cq: 



05 rt 



J4 



^2g 
c . 



OJ 



T3 
(L) 

"T 0) -= a, 



ei 



jS^ 



^ ba 

^ 03 

^ cr 



anS 03 ^ S 



>, O! 

ill 






1.1 

2i^ 

3 ^ 

o o 



c <u 
rt.tJ 

05X1 

«j c . 






!^S 



o 

4; S ■" a^— * 

•E.S||= 

to _, (u 3 (u 

o -o a 



152 MODERN TUNNELING 

being not uncommon) the general statement seems warranted 
that the hammer type has the greater speed in driUing the holes 
required in tunnel headings. 

It is difficult to determine just how much of this greater 
speed is due to the manner of attack, the water feature, the 
greater ease and speed in replacing a dull steel with a sharp 
one, or to the non-reciprocating drill steel, but there is Httle doubt 
that all these factors enter into the result. The piston machine 
when attacking the rock strikes comparatively slow, heavy, 
smashing blows that soon dull the cutting edges of the bit, 
especially if the rock be hard, after which, until the steel is 
changed, the penetration must be accompHshed by crushing. 
Conversely, the more frequent blows of the hammer type, being 
Kghter, do not dull the bit so quickly and the penetration is 
effected by a chipping action which is speedier as well as more 
economical of power. The application of water through a hollow 
steel to the face of the drill hole, in addition to cooling the drill 
bit and preserving the temper of its cutting edges, affords a 
positive means of removing the cuttings promptly from the 
front of the bit. This not only prevents the recutting and grind- 
ing of material already broken, with a consequent saving of 
power, but increases the efficiency of the machine, since it enables 
the drill bit always to strike an uncushioned blow on "live" rock. 
Hammer drills having the water feature, however, are said to 
make a poor showing when drilling vertical holes. This is 
doubtless due to the fact that the velocity of the rising current 
of water in the drill hole is not sufficient to prevent the rock 
grains from settling against it to the bottom of the hole and 
interfering with the work of the drill. The plunger action of 
the piston drill, on the other hand, while it is probably no more 
efficient in actually removing the rock grains, keeps them stirred 
up enough partly to obviate the difficulty. Any one who has 
experienced the trouble and delay of changing steels with the 
usual chuck in piston drills will appreciate the saving in time 
and energy resulting from the use of a chuck into which the drill 
needs only to be inserted. Since in the hammer drill the steel 
does not reciprocate, the elimination of friction against the sides 



I 



ROCK-DEILLING MACHINES 153 

of the drill hole effects a considerable saving of power and prevents 
a retardation of the blow, even though, as has been argued, it is 
partly offset by the loss of power in heating the hammer and drill 
end and in overcoming the inertia of the steel. An additional 
advantage of a non-reciprocating drill steel is the fact that it 
may be held against the rock at any desired point and a drill 
hole started wherever necessary without loss of time — a feature 
especially important where the face of rock is oblique to the drill. 

The weights of hammer drills range from 115 to 170 pounds, 
while the piston machines used in tunneling at the time the field 
examination was being made for this volume weighed from 
280 to 400 pounds, and the dimensions of the former were ap- 
proximately four-fifths of the latter. This gave the hammer 
machines an appreciable advantage over the piston drills because 
they were lighter, smaller, and more easily handled in a restricted 
space. The shorter length of the hammer machine also made it 
possible to start the cut holes nearer the sides of the tunnel, thus 
securing a wider angle between each pair with a consequent 
increase in the chances of breaking the full length of the round of 
holes. Since that time, however, the leading manufacturers of 
drills in the United States have produced and are marketing 
piston drills that compare closely with the hammer machines 
in size, weight, and ease of handling, thus reducing these ad- 
vantages in favor of the hammer drill. 

Piston and hammer drills employed in tunneling are ap- 
parently on an equal footing to-day as regards cost of drill 
repair parts, although until quite recently the former had some- 
what the advantage. From September, 1905, to March, 1906, 
hammer drills were employed at the Gunnison tunnel with a 
drill repair cost per machine of 13 cents per foot of hole drilled; 
but when piston drills were substituted the repairs were reduced 
to 3 cents per foot.* Two years later (September, 1907, to August, 
1908), in driving the last 3,000 feet of the Yak tunnel, the cost 

* In addition to the cost of materials, these figures include also a charge 
for the labor of the machinist making the repairs, which is not embraced in 
any of the valuer which follow. This fact must be considered in making 
comparisons. 



154 



MODERN TUNNELING 



of materials only for repairs to the hammer drills employed was 
but i}i cents, approximately, per foot of hole. At the Marshall- 
Russell tunnel, where hammer drills were employed, the average 
cost of drill repairs from June, 1908, to June, 191 1, was but i^ 
cents per foot drilled. Piston machines were used at the 
Strawberry tunnel from January, 1909, to September, 191 1, 
the cost for repairs being nearly 2% cents per foot drilled. 
On the Little Lake Division of the Los Angeles Aqueduct, where 
hammer drills were employed from July, 1909, to May, 191 1, 
the average cost of drill repair materials as shown by the table 
was but 24 cents per foot of tunnel excavated. Since each 
of the two machines in the heading drills approximately 8 feet 
of hole for every foot of tunnel excavated, the cost per machine 
per foot of hole is 1}^ cents. 



COST OF REPAIRS FOR HAMMER AIR DRILLS. LITTLE LAKE 

DIVISION, LOS ANGELES AQUEDUCT. JULY, 1909, TO 

MAY, 191 1 



Tunnsl 


Tunnel Excavated, 
linear feet 


Total Cost of Drill 
Repairs 


Cost of Drill Repairs 
per foot of tunnel 


iB South 

2 North 

2 South 

2A North 

2A South 

3 North 

3 South 

4 North 

4 South 

7 North 

7 South 

8 North 

8 South 

9 North 

9 South 

10 North 

ID South 

loA North 

loA South 


1,030 
926 
419 
460 

375 

864 

2,149 

448 

725 

1,911 

1,024 

225 

1,334 

777 

2479 

2,626 

1776 
1.373 
1,756 


$160.59 
180.72 

6475 

46.28 

55-50 

113.60 

505-01 

67.03 

215.48 

399.70 

493.46 

146.56 

530.52 

230.51 

404-94 

585-78 

577-24 
303-06 

359-27 


$0,156 
•195 
•154 
.10 
.148 
.131 
•235 
.149 
.297 
.209 
.482 
.651 
•398 
.297 
.163 
.223 

.325 
.221 
.204 



Average $0.24 

For 1910 and the first half of 191 1 the repair cost of hammer 
drills at the Carter tunnel was 2 cents per foot of hole. At the 
Lucania tunnel, the repairs cost }4 cent per foot drilled, 



ROCK-DRILLING MACHINES 155 

but the hammer drills had been in use only one month. 
The hammer drills at the Rawley tunnel were new also, the 
repairs from May, 191 1, to October, 191 2, averaging 1.9 
cents per foot of hole. These figures, which are based upon 
estimates furnished by managers or others in charge at the 
various tunnels, do not pretend to more than approximate 
accuracy; but they give a basis for comparison such as has been 
hitherto unattainable, although in making such comparisons the 
type of rock must of course be duly considered. 

In spite of the development of other t>^es of valve mechanism 
for air drills, the tappet valve, which was one of the pioneers 
in the field, possesses advantages which still keep it in demand 
for use on piston drills intended for certain kinds of work. Since 
it is unaffected by condensed moisture, which greatly interferes 
with the action of some other types, it is especially adapted 
for use with steam or with air containing a large amount of water 
vapor. Its distinctive advantage, however, is that its movement 
is positive; if the piston makes a stroke the valve must be 
thrown, hence there is no uncertainty in the action of the drill, 
no ''fluttering." 

The tappet drill is at a disadvantage when working in ground 
that will not permit of the use of a full stroke, because it is 
necessary for the piston to travel far enough to throw the valve, 
and hence too short a stroke is not possible. Then, too, as it is 
impossible to prevent some air being trapped in front of the 
piston and compressed after the valve is thrown, it strikes a 
cushioned blow. This is not always a disadvantage; in elastic 
and "springy" rock an uncushioned blow will not give the best 
cutting eft'ect, while in sticky material compression assists the 
piston in starting on the return stroke. The tappet is subject 
to strains and wear which necessitate specially hardened material, 
not only in the tappet itself but in the bearing surfaces of the 
piston. 

Under conditions that require a snappy, vicious blow with 
high air pressure, the ordinary air-thrown valve gives the best 
results. This feature makes it particularly applicable to hammer 
drills in which, because of the small size and weight of the ham- 



156 MODERN TUNNELING 

mer, it is essential that there shall be no cushioning of the blow, 
and it is customarily employed on such of these machines as are 
not of the valveless type. When used with piston drills, the 
air- thrown valve permits a variable stroke; it renders possible 
at will a change in length of piston travel and force of blow. The 
short stroke and light blow possible with this type of drill make 
it easy to start a hole or to drill through seamy rock. After 
the hole is under way, or if the rock is soKd, a full stroke is used 
to get the best efficiency from the machine. The air- thrown 
type of valve is not positive in its action, however, and is apt 
to be somewhat sluggish with air or steam containing much 
water. It is claimed for the butterfly type that it avoids this 
difficulty, as well as most of the troubles caused by freezing, and 
that it has a positive and at the same time a flexible action 
which permits of much higher speed than other valves. 

The auxiliary valve is designed to combine the advantages 
of the tappet and the air-thrown valves while avoiding their 
defects. The hghtness of the tappet auxihary is said to prevent 
the injury or retardation of the piston and also to obviate the 
rapid wear of rings, piston, and cylinders caused by crowding 
against the opposite cylinder wall due to an unbalanced tappet 
not readily moved. A drill equipped with this type of valve has 
a wide variation of stroke and delivers an uncushioned blow. 
The main advantage of the steel ball auxiliary valve is the great 
resistance to wear and the cheapness of replacing the wearing 
parts. It is claimed for this valve that it assures a positive action 
of the drill without sticking or fluttering, and yet possesses the 
necessary flexibility. 

The valveless method of regulating admission and exhaust 
has the advantage of simplicity and hghter weight due to the 
eHmination of the valve and valve chest. It also uses air ex- 
pansively, and this should result in economy of power. It 
strikes a cushioned blow, however, thus reducing the drilling 
power where the rock is hard and tough; but for medium rocks 
and especially with high air pressure the difference is said to be 
less pronounced because the lighter and more rapid blows chip 
rather than pulverize the rock and enable the drill to penetrate 



I 



ROCK-DRILLING MACHINES 157 

readily. One real disadvantage is the fact that as the cylinder 
becomes worn there is a leakage of air past the piston, thus 
increasing the air consumption and interfering with the accurate 
working of the drill. 

Hydraulic Drills 

Among the advantages of the rotary hydraulic drill 
used at the Simplon tunnel should be mentioned the fact 
that the power was delivered to the cutting edge without the 
shocks, jars, and strains due to percussion, thus eliminating 
one source of wear and tear. The machine also utilized a very 
high percentage of the power stored in the motive fluid, its 
efficiency being given by one authority as 70 per cent. Again, 
by passing a portion of the waste water down the boring tube, 
chips and debris were promptly removed from the cutting edge, 
thus insuring the maximum boring power. On the other hand, 
the pressure required for operating this drill was enor.mous, 
ranging from 450 to 1,200 pounds per square inch according to 
one writer, and 1,470 pounds according to another. In any case 
the piping necessary to transmit the water under such high 
pressures must have been most expensive to install and main- 
tain. The drill also required extremely heavy and rigid mount- 
ings to withstand the back pressure; these made it cumbersome 
and hard to move so that it could not be easily placed for a new 
hole. 

The percussion type of hydraulic rock drill cannot as yet be 
said to have been demonstrated to be a practical success. It is 
an interesting possibility, however; because, like the hydraulic 
ram, it utilizes the shock that occurs in pipes at every stoppage 
of ,a moving column of water. 

Electric Drills 

Among the advantages claimed for the pulsator type of 
electric drill are saving of power, rapid drilhng speed, simpler 
construction, and less trouble with fitchered drills. The motors 
which are used to operate the pulsator require, according to the 
size of drill, from 3 to 5 horse-power — a very small amount when 



158 MODERN TUNNELING 

compared with the necessities of the ordinary pneumatic drill. 
Although it is true that the cost of power used by a drill is not the 
only item which determines its efficiency, such a marked differ- 
ence in power consumption must necessarily exert a great 
influence. This fact holds especially in the case in hand, since 
it is claimed and apparently well substantiated by actual results 
that this machine is fully up to the drilling speed of any corre- 
sponding standard air rock drill and has practically the same 
cost for wages and fixed charges. The pulsator type also 
eliminates many parts, such as valves, springs, side rods, etc., 
which are sources of trouble and unreKability in other rock 
drills. It is able, moreover, to strike a very heavy blow because 
the pressure of air back of the piston is greatest just at the time 
of impact; and should the drill steel become caught in the hole 
from any cause the machine does not cease running, as is the case 
with air drills, but the pulsator continues to exert several hun- 
dred alternate pulls and pushes on the drill steel per minute; 
these in most instances are sufficient to loosen the drill at once, 
consequently saving considerable time and trouble. 

On the other hand, the combined drill and pulsator are 
cumbersome and occupy a large space, every inch of which is 
precious in the tunnel heading — a disadvantage that increases 
directly with the number of drills needed for the work. For 
tunnel work it is necessary either to place the truck and pulsator 
upon the muck pile — a feat consuming extra time and energy 
and a position where it is subject to damage and breakage if the 
muck is being removed simultaneously with the drilling — or 
one must wait until the tunnel is cleared of debris before starting 
to drill, a procedure which is prohibitive if speed in driving is 
required. But under circumstances where there is no particu- 
lar haste or in mining work where drilUng and mucking are 
alternated, this disadvantage is not so serious. 

The piston electric drill described on page 143 does away with 
the need of a pulsator, truck, and connecting hose, thus making a 
compact machine and one more comparable with an air drill. 
It is, however, quite heavy (weighing 490 pounds with the 
motor attached and 350 pounds without it, and is somewhat 



ROCK-DRILLING MACHINES 159 

difficult to handle and move in a small heading. It has a marked 
advantage over air drills in power economy, operating as it does 
on 4 horse-power, and actual results show that its drilling speed 
is fully up to that of standard piston pneumatic drills. At 
the Elmsford tunnel of the Catskill Aqueduct these drills are 
reported to have attained a speed of loo feet in six to eight 
hours when driUing in a comparatively soft mica schist, but in 
the harder Fordham gneiss of the city tunnel the rate was but 
60 feet per shift (eight hours) . This drill is still in the process of 
development, in which it is necessary to correct the small defects 
that always appear in any newly designed machine when put 
to actual use, but the results attained with it in one portion 
of the city tunnel, Catskill Aqueduct, were very encouraging. 
One of the machines is reported to have operated there for more 
than five weeks, drilKng over 4,000 feet of holes with none but 
minor repairs, such as pawl springs, etc. 

The weight of the air-cushioned hammer drill and motor 
described on page 144 is about 150 pounds less than that of an 
electric piston drill and motor. With the motor removed, 
although it weighs more than a pneumatic hammer drill, it is 
but Kttle heavier than a piston air drill of corresponding capacity. 
Its power consumption is rated at 2}^ horse-power and in the 
tests on the Catskill Aqueduct 6 to 8 feet per hour was the aver- 
age drilling speed attained in ordinary work, including delays. 
This speed will undoubtedly be increased as the delays from 
breakdowns become less frequent. The drill was still being 
tried out and in the process of being perfected at the time of 
examination, so no data could be obtained as to its reliability. 

The other air-cushioned hammer drill (see page 144) has been 
employed in several mines in Colorado, where, according to the 
testimonials, it is performing creditable service. 

The average power consumption of the rotary hammer 
drill (see page 146) is about i kilowatt per hour (iK horse- 
power). They were employed on the Elmsford contract of the 
Catskill Aqueduct and were reported as particularly efficient 
in comparatively soft rock, drilHng at times as high as 100 feet 
per machine in an eight-hour shift. 



160 MODERN TUNNELING 

CHOICE OF DRILL 

The factors to be considered in the selection of a rock drill 
for tunnel work are, on the one hand, the cost of power, of at- 
tendance, of maintenance and fixed charges, and, on the other, 
the rate of drilHng, the best drill being the one which combines 
all these factors in such a way as to develop the greatest drilHng 
speed for the least cost. The power cost should include not 
only the actual power at the tunnel plant (with its charge for 
labor, fuel, interest, and depreciation), but all losses in genera- 
tion, in transmission, and utilization in the drill. The wages of the 
drill-runners and all helpers required are just as much an item 
of operating cost as the charge for power. The cost for main- 
tenance includes the cost of repair parts for the drill and the 
charge for the time of the machinist, together with the cost of 
sharpening drill steel. The fixed charges should include interest 
and depreciation on the cost of the drills and a proportion of the 
administrative expenses. The rate of drilling, on the other hand, 
should not be based upon the speed of penetration while the drill 
is actually hitting the rock, but should include all delays caused 
by the drill, such as loss of time in preparing the set-up, 
in shifting position to new holes, in changing drill steels, and 
any other interruptions properly chargeable against the 
machine. 

Applying these specifications to the various rock-drilling 
machines, the hammer pneumatic drill is apparently the one best 
adapted for use under ordinary conditions in driving mine adits 
and tunnels. To be sure, its power consumption is more than 
that for electric drills, but it is about equal to the hydraulic and 
is less than the piston air drill. In the matter of attendance it 
has somewhat the advantage. Most of the piston air and the 
electric types usually require at least two men to operate each 
drill — a drill-runner and a helper — and the hydraulic machine 
requires five men.* With the hammer drill a runner is necessary, 
of course, but one helper often is able to attend to two drills 

* Prelini, "Tunneling," p. 105. 




ROCK-DRILLING MACHINES 161 

or two helpers to three machines. We have just seen that there 
is practically no difference between the piston and hammer air 
drills as to repair cost. The multipKcity of parts in the rotary 
hydraulic machine, however, is said to have been a source of 
much trouble in this respect. Theoretically the hammer drills 
do not dull the steel so rapidly, and hence should have an ad- 
vantage in this respect. Practically this is not an important 
difference because under ordinary conditions the blacksmith 
is rarely overtaxed, and hence the extra labor of sharpening a few 
bits more or less is not noticeable on the cost report. The fixed 
charges are such a small portion of the total cost of drilling that 
any discrepancy in them is rarely, if ever, large enough actually 
to decide the question. The rate of drilling is really the 
greatest factor in favor of the hammer type ordinarily 
used in tunnels. Not only does it penetrate faster when ac- 
tually drilling, but, since its reciprocating parts are lighter 
and its vibration less than that of a piston machine, it can be 
employed with a lighter set-up, with a saving of time. Then, 
too, its ability to start a hole at any desired point and to 
drill rapidly holes that point upward enables it to be used ad- 
vantageously on a horizontal bar with a saving of the one-half 
to one and one-half hours which are required to remove the 
debris before setting up the vertical column used almost without 
exception in tunnel headings for piston air drills. The hammer 
drill saves not only time in changing drill steels but energy as 
well, as any one who has wrestled with the ordinary piston 
chuck can testify. 

For large tunnels excavated by the heading and bench 
method and in which a large number of holes are drilled down- 
ward, or perhaps at other places where, because of acidity in the 
mine water or some other reason, the water feature of the 
hammer drill would be unsatisfactory, or for other work than 
tunneling, the piston pneumatic drill would doubtless give 
equally if not more satisfactory results. Or if speed is not 
especially required and the drilling and mucking shifts can be 
alternated, the pulsator electric drill with its large power economy 
might prove the most efficient. And again, if the self-contained 



162 MODERN TUNNELING 

electric drills continue to be improved as they have been recently, 
their greater economy of power will without doubt soon out- 
weigh their lower driUing speed and present higher maintenance 
charges, especially at such places where electricity is readily 
available. On this account their development should be closely 
watched. 



CHAPTER IX 
HAULAGE 

TUNNEL CARS 

Most students of tunneling methods concede that an essen- 
tial, and possibly the chief, feature of the problem is the rapid 
removal of debris produced in blasting; but it is commonly not 
so well recognized that the speed with which this may be ac- 
comphshed is greatly influenced by the size of the tunnel-car. 
Large cars, even when empty, are heavy and cumbersome, but 
when full of rock they can be handled only with the greatest 
difficulty. To remove such a car from the heading and replace 
it with an empty one requires either several extra men to assist 
in the work or a horse or mule must be provided for the purpose. 
In the first instance men must be called upon who might other- 
wise be making arrangements for the rapid loading of the next 
car or doing any of the many things that make for speed and 
economy; while in the second, omitting altogether from consider- 
ation the cost and maintenance of the mule, delays and loss of 
time cannot be prevented. In addition to being unwieldy, 
large cars occupy a greater proportion of the actual space in the 
heading, constricted enough at best, thus preventing the shovel- 
ers from working to the best advantage ; the added height involves 
a waste of energy because each shovelful of rock must be lifted 
a greater distance, making it impossible for the men to handle 
sufficient material in a given time. With large cars it is neces- 
sary to maintain a switch or siding near the end of the tunnel 
in order to permit the empty cars to pass the loaded ones, and 
time and labor must be expended frequently in relocating the 
switch nearer the heading to keep pace with the tunnel advance. 
The smaller car, on the other hand, when empty can be tipped 
off to one side out of the way and replaced easily when needed, 
thus giving a clear track for a loaded car and obviating the 

163 



164 



MODERN TUNNELING 



necessity for a switch. In case of derailment, an occurrence 
by no means rare in practice because of the poor condition of 
most tunnel tracks, the large car, even when empty, is harder to 
replace, and when full it is sometimes necessary to unload all the 
material in order to get the car back on the track. It is true 
that a larger number of the smaller cars, each of which occasions 
some delay in its arrival and departure, are necessary to remove 




n 



Fig. 46. Elevation of tunnel car used in the east end 
of the Gunnison tunnel. 



the same amount of debris, but the authors are of the opinion, 
based upon a study of actual conditions at a large number of 
tunnels, that with proper organization greater progress is at- 
tainable by using smaller cars, the size preferred being from 15 
to 25 cubic feet capacity. The tendency at many American 
tunnels is toward the use of cars much larger than this, especially 
where electric haulage is employed; but the use of large cars, 
when analyzed, has been shown to be a handicap rather than an 
advantage even in those tunnels equipped with them where 
creditable progress has been made. 

In design, the cars at a majority of the tunnels visited 
follow the standard mining types with tilting bodies, but at a 
few of them other types were employed to meet special condi- 
tions. A car with a side-dumping, tilting-box body was used in 



HAULAGE 



165 



the west end of the Gunnison tunnel. End-dumping cars are 
similar to this except that the hinge is transverse instead of lon- 
gitudinal and the door is situated at the end instead of the side. 
The car used at the Laramie-Poudre tunnel, which is illustrated 
in Figures 48, 49, and 50, was of the turn-table type, which per- 
mitted dumping from both sides of the track as well as between 
the rails. As the system of car handling in the headings at this 
tunnel necessitated throwing all of the cars over on their sides 
once (and nine-tenths of them twice) on each trip, the connec- 
tions between the trucks and bodies of the cars were carefully 
planned and made unusually strong. The turn-tables were fitted 
with two concentric rings (Figures 49 and 50), and the locking 
mechanism for securing the bodies to the trucks was so designed 





^' 




^1 ..'■•<./" 1. 









• 


! 

1 


•1 




i. 




•1" . 




• .r 






: 


s 




f 


1 














< — 


2'0" 







Fig. 47. End view of tunnel car. 



that when the releasing lever was fastened in place the cars were 
as rigid as if the bodies were riveted to the axles. A car of the 
rocker type (see Figure 51) was used with very satisfactory results 
in the tunnels of the Los Angeles Aqueduct. At the Nisqually 
tunnel a similar car, but one with a sHghtly different locking 




Fig. 48. Elevation of tunnel car used in Laramie-Poudre tunnel. 




t^ 18 Track gage >H 

Fig. 49. End \'iew of tunnel car. 







.Mr- 



:_4fh:J6"i'inTf'T ' I 



fe:^i^rrEi^ 



i i'i\V^. 



\\ ' III nrnj 1 1 1 



,mi 



m 
KO 



© 



Fig. 50. Plan of tunnel car. 



Compression-spring ^—^ 
drawhead cast steel '^ p 

i — 






IL. 


jr 
















- 


1 1 






] 1 






1 ^ 


1 

E 














l< — ^1 


■^^— 1 


- 




1 =^ 








||Kp^o|o 


0^] 






-^ <J 


^ 





i ° 



g s 

■7 "9 



o o 

o o 

bp to 





V'/'' 


1 


'i\V. 


c 


1 

o°o°o 


^ 


1 ]]°o°o°| 


7 






Fig. 51. Rocker dump tunnel car used on Los Angeles Aqueduct. 



168 



MODERN TUNNELING 



device, was employed. (See Figures 52 and 53.) In order to 
obviate the tilting body, the car at the Utah Metals tunnel was 
constructed with the floor permanently inclined toward the side 




Fig. 52. Tunnel car used at Nisqually tunnel. 




Fig. 53. Method of dumping tunnel car. 

door, while at the Carter tunnel a car of the gable type was used, 
in which the floor slopes away from the center toward doors on 
each side of the body. At the east end of the Gunnison tunnel 



HAULAGE 



169 



a 




E 




3 




-o 




i" 


>, 


u 


L 


cd 


o 










u 


01 




Si 


03 


^ 


II 



3 


G 


TJ 


3 




T) 






O 


^ 


i_ 


TJ 


o 


?^ 


p 


u 



3 
bfl 



a 

a o 
Qc75 



^ o 





CJ 




c; 




c; 
















03 


(1) 




flj 




Cl) 




















3 


o 


3 


o 


3 


a; 


r 



c 

03 U U 



U U U ^^ O 



O 03 






Si ^wSu^^uj<EX 






o — u o 



i- 5^ y iri-:^ 



^ _) ^ -* _ii ^ O O^^ 









wwd:swwwSd:<wxxwwu 






O O vO Tl-00 O 00 >+ "^ ^ Ti-OO C4 






rfri-Td-POnoOi-. -wrDiOi-iOO 






3 S 
O 03 



a 
E 

3 

13 

C 



E S E-S 

3 3 3 iS 

"VV? c 

^^ C 3 

c/^ Lo W H 



i- 

^ +j 3 '^3 



ii ^ a 



a 
E • 

3 

c 
V a, 

^2 



E E 

3 3 

aaag g 

E E E - •> 

— '. H ~ (11 o 



a a a 
E E E 
:2 a :2 

yyy 

o c c c 



face-- fa--- 

3 3 3-^ -Si a 3-^^^aaa 

-o-u-u-Q^ E -uxjxijo E E E 

,' ,'..'. rt o3 -( ,'. 03 o3 o3 3 -3 -1 



03 rt cti _ _ 



TO CO "3 
O O O Y Ytd - . 

OOOl-.l-,aJXCJt- 

O O O 3 3^3 O O 3 3 3 i^ C"W O '-' W 



t: t oj-ujJ X 



E E 

3 3 

i i 



>- ^ T-^ Js X ^ Ji 



it: t: 

3 03 

fflU 



3 

=2 o 
en 
OS 

u 



— 03 

=! O . 

03 O—. 



a en' 

O 5 t« 



en -a 

03 3 






< o3ir-£ 

en hj -^ o 
V-^ ao3 






■liaC4-.'TDC§^rten^'-"-"^a32w^ CT^ F J5 rt -^ ^ 
C'-^u-T---='03^^i-3en oi3en^Sn^>iOtifrtjC 



>^ OJ 



170 



MODERN TUNNELING 



(see Figures 46 and 47, pages 164 and 165) a simple open box 
car with the body bolted directly to the truck was employed, and 
similar cars are now in use in the Strawberry and Newhouse 
tunnels. Although this car is ideal from the viewpoint of sim- 
plicity, it requires special equipment for dumping because the 
entire car must be turned completely over. The table on page 
169 contains suggestive data concerning the cars used in tunnels 
and adits in the United States. 

LOADING MACHINES 

Many attempts have been made to utilize machinery for 
loading tunnel cars. In several of the larger tunnels intended 
for railway purposes, power shovels similar to those used in grad- 
ing or in open-cut mining have been very successfully used in 




Fig. 54. "Mucking machine" at the Hummingbird tunnel, 
Burke, Idaho. . 



removing the broken rock of the bench after blasting. In such 
cases the ordinary steam shovel is generally employed, making 
a few minor alterations so that it can be operated by compressed 



HAULAGE 171 

air. Power shovels operated by compressed air are also employed 
in some of the mines in the JopHn, Missouri, district. 

The ''mucking machine" illustrated in Figure 54 was used 
successfully during the excavation of the Hummingbird tunnel, 
at Burke, Idaho. Its principal feature is an oscillating trough 
or shovel armed with teeth and driven by a compressed-air 
piston in such a manner that the forward stroke is appreciably 
faster, than the return. When in operation the teeth rest upon 
a steel plate under the muck pile, and as the shovel is fed forward 
the broken rock is forced by the jerky motion backward along 
the trough and discharged upon a belt conveyer which dehvers 
it to an ordinary mine car at the rear. The entire machine is 
mounted upon a wheeled truck or framework and is fed forward 
by a second compressed-air piston connected with a cross-bar 
which can be jacked against the sides of the tunnel. It is 
essential that the area of this piston be smaller than the one 
which drives the shovel; for then, if the latter encounters a 
boulder or other obstruction too solid for it to dislodge, the 
entire macliine can move forward and back with the stroke of 
the larger piston. By this means the machine is not only 
prevented from injury before the obstruction can be removed, 
but in many cases it will work the boulder aside without any 
assistance. One man is required to operate the machine, and two 
more are needed to tram the car to and from the end of the 
conveyer and to shovel the rock out of the corners of the tunnel 
into the trough, for the machine does not swing from side to 
side, but merely cuts a swath down the center of the tunnel, 
and hence leaves a certain amount of material piled on each side 
of it. The machine is reported to have reduced the time re- 
quired to clean the tunnel from 6 to 2^ hours and to have made 
it possible to increase the speed of driving quite materially. 

The shovehng machine illustrated in Figure 55 is very 
ingenious and closely simulates the actions of a man shoveling. 
At the front is a scoop or shovel, armed with teeth, which is 
pushed under the broken rock and raised by the action of a 
chain-driven crank, so that the material is dumped into a hopper 
just back of the shovel. The hopper in turn travels a short 



172 MODERN TUNNELING 

distance, tilts up, and dumps the rock on a belt conveyer which 
deHvers it to cars at the rear. The machine was employed ad- 
vantageously during the excavation of a portion of the Catskill 
Aqueduct directly under New York City. In this work six 
men were employed with the machine; one to operate it, three 




Fig. 55. Shoveling machine. 

to pick down the muck pile in front, and two to handle cars in 
the rear, as compared with the usual crew of fourteen men when 
mucking by hand. The power consumption was 25 to 30 kilo- 
watts per shift. The machine would pick up a rock that 
ordinarily would take three men to put over the side of a car 30 
inches high and a car holding 35 cubic feet could be loaded in 



A power loader of a somewhat different type was introduced 
in the excavation of the bench at the Yonkers Siphon. It 
consisted of a chain-and-bucket conveyer, similar to that used 
in mill elevators and on some gold dredges, which delivered the 
material to a hopper, whence it was carried to the tunnel car by 
a fiat endless belt. 

Owing to the hardness of the rock and the prevalence of huge 
boulders, weighing sometimes over a ton and necessitating 
frequent stops for repairs, this machine was unable to compete 
satisfactorily with hand loading underground. When operating 
on the surface, however, loading rock for use in concrete con- 
struction it is said to have given excellent satisfaction. The 



HAULAGE 173 

material was taken from the dump pile produced in excavating 
the heading of the tunnel in which the rock was broken more 
uniformly into smaller fragments than the material produced 
in blasting the bench. It should be mentioned, however, that 
the size of this machine precludes its use without considerable 
modification in a small tunnel or heading. 

MOTIVE POWER 

In practically all tunnels of any length in the United States, 
either animals or electric motors have been or are employed to 
haul the tunnel cars. In Europe, notably at the Simplon and 
Loetschburg tunnels, compressed-air locomotives were used 
successfully. But although those machines are employed to 
some extent in this country in mining and industrial work, they 
have failed to give satisfaction at tunnels where they have 
been tried, chiefly because of the cost of high-pressure air, the 
maintenance of charging stations, the time lost in charging, etc. 
Many mines also are equipped with cable haulage; but because of 
the constantly increasing length of haul as the heading advances, 
the use of this system in tunnel work requires such frequent 
delays and loss of time in extending the cable system that it is 
hardly suited for tunnel practice. Gasoline locomotives, on the 
other hand, which have recently proved most successful for coal 
mining, are in most particulars especially well adapted for tunnel 
work and deserve equal consideration with animals and electric 
motors as a means of tunnel haulage. 

The principal advantage of animal haulage is the smaller 
cost of installation; what is more, it requires no special intelh- 
gence on the part of the driver, and the ability of the animals 
to step across the track at the tunnel headings obviates the 
necessity of a switch. On the other hand, the costs of main- 
tenance and operation for animal haulage not only are high, 
but these factors go steadily on whether the animal is working 
or not and are influenced but slightly if at all by the amount 
of tonnage handled. For these reasons animals are not economi- 
cal for use in long tunnels because the saving in installation 
expense is soon destroyed by the increased operating costs. 



174 MODERN TUNNELING 

Then, too, the odors arising from the track are offensive and 
disagreeable when animals are employed and their respiration 
vitiates the underground atmosphere, necessitating more ample 
ventilation. As far as efficiency is concerned, there is little if 
any difference between horses and mules, although the latter 
are considered by some to be the sturdier animals. Mules, 
however, are better fitted for work in low tunnels because they 
are usually somewhat smaller than horses and, being less nervous, 
do not throw their heads violently up and back when anything 
touches their ears. 

Electric mine locomotives may be divided into two classes: 
those operated from a trolley system and those obtaining their 
electrical current from a storage battery. The former are so 
familiar as hardly to require description. They generally consist 
of two motors, ruggedly constructed to withstand rough usage 
and protected from dust and moisture, mounted upon a cast-iron 
or structural steel frame which also carries the trolley, controller, 
rheostat, and other accessories. The sides of the frame may be 
placed either inside or outside of the wheels. In the latter 
type more space is available for the motors and other equipment 
and the various parts of the machine are more readily accessible. 
The inside type, on the other hand, has a smaller over-all width 
and is therefore more suitable for narrow tunnels. The storage 
battery locomotive is similar in most respects to the trolley 
machine, except that provision must be m.ade for carrying the 
necessary batteries. In most cases the batteries are carried 
directly upon the motor itself, but the locomotive installed at the 
Central tunnel is somewhat unique in that the batteries arc- 
placed upon a separate battery car or tender. When the 
machine is handling cars in this tunnel it obtains its current 
from the battery; upon reaching the tunnel mouth, the tender is 
left on a side track, w^here it is accessible for recharging, and a 
trolley, with which the locomotive is also equipped, is employed 
for switching. 

Electric locomotives are compact and simple in construction 
and do not emit smoke, gas, or disagreeable odors. They are 
more rapid and are capable of hauHng a much greater load than 



HAULAGE 



175 



either a horse or a mule, while the cost of . the power used is not 
nearly so great as the cost of forage. But, on the other hand, 
they require the installation of extra machinery in the power 
plant, an expensive trolley- wire or a troublesome storage battery, 
and the road-bed and track must not only be heavier in con- 
struction, but usually the rails must be bonded to make them 
good electrical conductors. The disadvantage of the cost of the 
extra electrical machinery is of course partly offset by the fact 
that it can be utilized also to operate the ventilating machin- 
ery and to furnish illumination for the tunnel. The use of 
trolley wires in the restricted tunnel space, however, introduces 
the grave danger of serious and perhaps fatal injury to persons 
accidentally or ignorantly coming in contact with them. 

GasoHne locomotives consist essentially of a frame, as a rule 
of cast-iron, upon which are mounted the gasohne engine (usually 




Fig. 56. Gasoline mine locomoti 



4-cylinder), the necessary transmission system containing gears 
and clutches, together with the carbureter, magneto, cooling 
system, and other accessories. In external appearance (see 
Figures 56 and 57) they are not unlike the electric locomotives 



176 MODERN TUNNELING 

described above. Two forward and two reverse speeds are 
usually provided in the machines manufactured in this country, 
the lower one of 3, 4, or 5 miles per hour, and a higher speed 
double that of the lower. The draw-bar pull ranges from 1,000 
to 4,000 pounds, according to the size of the locomotive. In 




Fig. 57. Gasoline mine engine. 

some of the machines the exhaust gases from the engine are 
passed through a tank containing a solution of calcium chloride, 
which cools the gases and is said to remove all offensive odors 
from them. In a German-made machine the exhaust gases are 
sprayed with water to produce the same effect. 

The gasoline locomotive combines most of the advantages 
of both electric and animal haulage. It is self-contained and 
independent of a central station or any other outside source of 
power, needing nothing but a track. It is fully as rapid as the 
electric motor ordinarily used in tunnels and is capable of 
handling an equal load. The fuel for a gasoHne locomotive can 
be obtained readily in almost any locality, and the machine does 
not consume fuel when it is not running, a matter of great 
importance in tunnel work, where interruptions occupy a neces- 
sarily large percentage of the time. Another advantage, although 
perhaps not so important for tunnel work, is the fact that the 
haulage system may be expanded by the addition of extra 
units without alteration in the power plant, hence the possibility 
of such future changes need not be considered in the design of 
the power plant. The following table, based upon replies from 



HAULAGE 



177 



o 
< 

< 

X 

u 

o 

< 

o 

o 

H 
on 

O 
U 

O 
g 

< 

Pi 

o 



••03 3uiuip\[ 1B03 apBqs 




ON 


oT 




"0 


NO NO 

00 10 

10 


10 




i 


'•ooSuiuipv IB03 30junj\j 


m <-< "^ 


n »o 

4^ 


10 


s ^ 


8 


•^d 'uoiJnqiiM 
•03 |B03 AaiiBApiiv 


^ <N 


10 

(N « '^ 
CO »0 M 


fN NO 
10 


? 


f 


'•03 IB03 uapiv 


ir> 10 


ON 

r^ vo Qo 


^ 10 


8§l, 

- 03 




1 

•^A-A\'ppyj3po-a 

'•03 35103 :81B03u3q3nBA 





vO 

rO i-< 
00 NO 10 


Ss 8 

Ov 






•UU8X 

'A;i3 Adbjx '•03 P03 

pa;BpilOSU03 33SS3UU3X 


■^ 10 »o t^ 

ON »0 


to 

4^ 


10 10 

NO r< 


iT 


00 

P-H 

q 


j 

•BJ •BJ3pBp\[ 

'•03 :^ adoMg 'a "H 


« n 


10 10 

4^ 


to '^ 

00 


00 

q 10 




q 




oc 


3 ON vo 'xt- 

ro -, 

00 

10 


8:?oo 

NO to 10 

4^ 


10 


- CJ 




'•03 uoji auBo-a 




'•031B03 

SSapiJOUlS SB^UOlJBDOd: 


'^ 10 lr> - 


fo ^10 


10 ON 

NO 


<N 10 

q (Nj 


S 


"03 1B03 uosjapuan 


10 


1000 

y^ 10 


n NO 

rO NO 

NO 


i ^ 


q 


•UU3X 'B3COUB35B113 

■•03U0Ji28iB03mBqana 


ON n VO 


ON 10 

vq 10 


to 

00 





ro 


'III 'uo:)u3JX '"03 
! SuiuiK uo;u3JX-9S33Ja 


ON >- 


100 

lo^ Os 




to rh 

00 








c 

c 



Average number of trips 
each locomotive 

Average gross tonnage 
loaded trin 


<L1 

c 
c 


en 

-So 
< 


3 

"o 

- c ^ 

^ > 

- rt 


2 

B 

D 
G 

< 




-a > 


Cost of labor per day .... 

Cost of lubricating oil per 
day 

Operating cost, exclusive 
of repairs 

Cost per ton mile, not in- 
cluding repairs 

Average daily cost for 
repairs 

Cost per ton mile, in- 


2 

■§ 

bi 

c 

z 


D 



178 MODERN TUNNELING 

operators and users of gasoline locomotives received in answer 
to inquiries sent out by the Bureau of Mines, in 191 2, shows 
the cost of haulage with these machines. 

Practically the only disadvantage of the gasoline locomotive 
is the amount of carbon-dioxide given off in the exhaust from 
the engine, but this can be eliminated by proper and adequate 
ventilation. When the machine is properly regulated the 
amount of carbon dioxide should not exceed 2^ to 5 cubic 
feet, depending on the size of the engine. If this were confined 
in a small unventilated space the air would soon become unfit 
for breathing, but since the greater part of the time the motor 
is traveling back and forth in the tunnel and since a large 
volume of air is, or at a properly organized tunnel should be, 
supplied by the ventilating blower, the exhaust gases from the 
engine are quickly diluted to harmlessness. It is essential, 
however, that the blower be arranged to deliver the air to the 
heading through the ventilating pipe, rather than through 
the tunnel, in order that the air may reach the workmen as 
pure as possible, and it would doubtless be necessary to run the 
blower somewhat nearer its capacity. But even were it operated 
at full load, the added cost of doing so would be more than repaid 
by the saving effected by the gasoline haulage. 

DUMPING DEVICES 

The box cars used at the Strawberry tunnel were dumped 
b.y an electrically driven stiff-leg derrick. The hook in the 
derrick block carried a bail which engaged trunnions, one at 
each end of the car. The trunnions were placed in such a way 
that when an empty car was picked up by the bail the weight 
of the running gear would be sufficient to hold the car upright, 
but if the car was loaded its center of gravity would be above 
the trunnions. A spring-actuated pin, situated in one leg of the 
bail and engaging a hole in the car body above the trunnion, pre- 
vented the car from overturning until it was swung out over the 
place where the rock was to be deposited, when by pulling a 
rope the attendant could disengage the pin and permit the car 
to turn over and deposit its contents. It would then auto- 



I 



HAULAGE 179 

matically right itself and could be swung back on the track. 
The derrick was mounted on wheels so that it could more easily 
be moved ahead, but this was necessary only at intervals of 
three to six months. 

Among the advantages claimed for this system of dumping 
is the fact that it could be operated by the train crew, the motor- 
man running the hoist and the brakeman adjusting the bail, thus 
saving the labor of a dumping gang. Then, too, it gave a much 
larger dumping area with a consequent saving of the time which 
with the ordinary mine car is lost in shifting tracks, etc. But 
this was offset in part by the setthng of the dump, and on this 
account the moving of the derrick was accompKshed with great 
difficulty. It is probable that some of this annoyance could 
be avoided at a future installation by using very wide wheels 
similar to the type used on roller trucks for moving houses. 
But the derrick is expensive, costing when erected at the tunnel 
approximately $3,600, of which hardly more than $1,500 could be 
reahzed from its sale after the completion of the work; for this 
reason its use must extend over a considerable length of time in 
order that the saving in wages may repay the original cost. 

At the Newhouse tunnel the loaded cars were run into a 
cylindrical steel framework having rails at the bottom and a set 
of angle-iron guides at the top with just enough clearance space 
between them to hold the car firmly. The entire apparatus was 
then revolved by an electric motor until overturned, emptying 
the contents of the car, and it was then righted by continued 
revolution and the car removed. Although used here only for 
ore cars, the material falling into a bin for shipment, it offers 
a satisfactory and reasonably inexpensive means of dumping the 
more durable soHd body and tmck cars, and could doubtless be 
applied to tunnel dumps by the use of a light trestle or similar 
structure. 

Almost an}^ of the various cradle dumps frequently used at 
coal mines can readily be adapted to tunnel work by mounting 
upon a stout frame of logs or large timbers, which could be 
pushed forward along the top of the rock pile as necessity arose. 
By this means it is possible to eliminate hinges and turn-tables 



180 MODERN TUNNELING 

between the body and the truck of the car, thus simphfying 
and strengthening its construction. One of these cradle-dumps 
was used at the Lausanne tunnel. It was not expensive and 
saved a considerable amount of time in dumping cars and in 
keeping the rock pile in proper condition. It was pushed 
forward by the motor every two or three days, requiring but a 
few minutes for the operation. A similar dumping device is 
used at the Cameron mine, Walsenberg, Colorado. It has the 
added advantage of being mounted on a turn-table, thus giving 
nearly double the top width of dump attainable with ordinary 
cradle devices. As described in Mines and Minerals,"^ the 
dump consists essentially of three plates of one-eighth inch 
iron 3 by 4 feet in size. To the top plate are bolted a pair of mine 
rails with the ends bent up into horns. This upper plate re- 
volves on a mine car axle, the bearings for which are supported 
upon a mine rail and bolted to the middle plate. A piece of 
channel iron is bolted to the middle plate and upon it the dumper 
falls back after a load of rock has been discharged. The upper 
plates as a unit revolve upon the two annular pieces of iron, 
22 inches in diameter. The king-pin is i inch in diameter, and the 
plates, where it passes through them, are reinforced by a piece 
of }4- by 3 -inch bar iron. The lower plate is supported by four 
short lengths of 12-pound mine rail. 

* October, 191 1, p. 158. 



CHAPTER X 
INCIDENTAL UNDERGROUND EQUIPMENT 

TUNNELING MACHINES 

Although tunnels have been constructed for mine drainage, 
irrigation, and supplying water to cities for thousands of years, 
they were so few in number during ancient times and constructed 
at such irregular intervals that there w^as no great incentive to 
improve upon the methods ordinarily employed in driving them. 
With the advent of the steam railroad, however, it w^as soon 
realized that the desirabihty of maintaining easy gradients 
would necessitate the driving of many tunnels, and the active 
minds of inventors were immediately directed toward the prob- 
lem of making a machine which would do this work more or less 
automatically. 

The first tunneling machine of w^hich any record could be 
found was constructed at Boston in 1851 for use in the Hoosac 
tunnel. It weighed 70 tons and was designed to cut a circular 
groove in the face of the tunnel, 13 inches w^ide and 24 inches in 
depth, by means of revolving cutters. The trial of this 
machine in the tunnel proved unsuccessful, and only a distance 
of 10 feet was cut with it before it was abandoned. In 1853 
the Talbot tunnehng machine, which was designed to make an 
annular cut 17 feet in diameter and leave a cyHndrical core to be 
removed by blasting, was tested near Harlem, New York, but 
also proved unsuccessful. Later a smaller machine was con- 
structed, adapted to cut an 8-foot annular groove; this, while 
it was less unwieldy than its predecessor, also proved a com- 
plete failure after $25,000 had been expended upon it. Although 
numerous machines constructed upon almost every conceivable 
principle have been experimented with since 1853, the entire 
disappearance of most of them from sight, and almost from 
history, tells only too clearly that the problems of driving 

181 



182 MODERN TUNNELING 

through hard rock have been too difficult for the machines to 
overcome successfully. 

It is not safe to predict from this, however, that a tunnehng 
machine will not, or cannot, be constructed to perform this 
work in the future because, difficult as the problem of designing 
such a machine appears, the obstacles in the path are no greater 
than they have been in scores of other instances where slow and 
costly manual methods have been superseded by less expensive 
and more expeditious mechanical processes. The invention of 
some new rock-cutting device, or the material improvement of 
some of those now known, may simplify the problem to such an 
extent that the construction of a successful tunneling machine 
will be rendered comparatively easy. Further encouragement 
is also to be found in the fact that there have been two machines, 
designed for driving in the soft chalk formation underlying the 
Enghsh Channel, that have done practical effective work. 

The first of these is generally known as the Beaumont machine, 
because, although invented by Major English, it was developed 
and operated by Major Beaumont, of the EngHsh Army. This 
machine, which was not completed until 1883 (although patented 
as early as 1864), during a series of tests drove an aggregate of 
more than 6,000 feet of cylindrical tunnel 6^ feet in diameter. 
The maximum rate of progress attained was 81 feet per day, or 
40 inches per hoiir. During the final test an average of 50^ 
feet per day was maintained for fifty-three consecutive days. 
The machine was afterward tested in the Mersey tunnel at Liv- 
erpool, where it made an average speed of 30 feet in twenty-four 
hours in soft red sandstone and a maximum of 40 feet per diem. 
As the Beaumont machine can be used only in soft rock, a 
description of its mechanism is hardly necessary here, but its 
record shows what can be accomplished in mechanical tunneling 
by a machine carefully designed for the work it is intended to 
perform. 

The first patent on the B run ton tunneling machine was 
issued July 21, 1868; since then a number of patents have been 
granted for different improvements. While this machine, like 
the Beaumont, was designed primarily for driving in the chalk 



INCIDENTAL UNDERGROUND EQUIPMENT 183 

formation under the English Channel, it was the direct out- 
growth of the investigations and improvements on stone-cutting 
tools by the Brunton and Trier Engineering Company. The 
success of their stone-dressing machinery, now so largely used 
in this country and Europe, is due in a great measure to the 
perfection of the peculiar cutting tool which was employed in 
the tunneling machine, and which is described fully in an article 
on ''Modern Stone-Working Machinery," by M. Powis Bale, 
in Fielden^s Magazine for August, 1900, from which the following 
quotation is taken: 

"The cutters are of steel and circular in shape, somewhat after 
the form of a saucer, and have a rolling motion when in action, con- 
sequently the great friction resulting from dead pressure is done 
away with, the cutters having what might be termed a rolling wedge 
action. This system of rolling cutters was patented some years 
ago by Messrs. Brunton and Trier, and the pith of the invention may 
be said to consist in giving the circular cutters a determinate motion 
on their own axis, at the same time they are carried around in a circle, 
their cutting edges describing a circular path and the rates of cutter 
rotation and movement around the circle being so adjusted relatively 
one to the other that the cutting edge rolls in a slowly advancing cir- 
cular path." 

The pressure of the sharp wheel against the rock causes the 
latter to spring off the side of the cut in the form of spawls, 
very much on the same principle as a sharp-edged wheel-tire will 
throw a line of chips when passing over a sheet of ice. As there 
is no percussion, the machine works steadily and quietly, even on 
the hardest rock, and the durability of the cutting disks is some- 
thing phenomenal. 

Good descriptions of the Brunton tunneling machine may 
be found in the following: 

Drinker's ''Tunneling," pages 191-194. 
Zwick's "Neuere Tunnelbauten," page 68, with cuts. 
Johnson, Wm.: "Brunton's Heading Machine," Proc. Chester- 
field and Derbyshire Engineers, October 2, 1875. 
Engineering, Vol. VII, page 355, May 28, 1869. 

The machine was thoroughly tested out on both sides of the 
Channel, where it drilled an aggregate of approximately 8,000 



184 MODERN TUNNELING 

feet, and it was found that a seven-foot machine would bore a 
tunnel and load the cuttings on dump cars at the rate of 30 
inches per hour. Several thousand feet of tunnel were also 
driven with this machine in somewhat harder rock, but before it 
could be fully developed and placed upon the market further 
progress was stopped by the unfortunate death of the inventor. 

Any future tunneling machine, to be successful in hard 
rock, will have to be simple, durable, not hable to derangement, 
easily guided and controlled, and with all parts readily accessible 
for removal, adjustment, and repairs. It must be so designed 
as to permit the automatic removal and loading of the cuttings 
and at the same time afford free access to the face even when 
it is in operation. All actuating machinery and bearings must 
be completely housed and protected from mud and water and 
the framework so constructed that it will not be thrown out of 
alignment or its advance checked by openings or softened 
places in the rock. It must also permit of easy removal to and 
from the immediate face of the tunnel. Viewed in the light 
of present development, this seems a difficult problem, but the 
invention of some new cutting device or material improvement 
in some of those now known may so simplify the task that the 
construction of a successful tunneling machine for hard rock will 
be rendered comparatively easy. This has been the course of 
invention in numberless instances, and we have every reason to 
expect that here, as elsewhere, history will repeat itself. The 
simple device of putting an eye in the point of a needle made 
the sewing machine possible; the breech-loading gun was a com- 
plete failure until the brass cartridge was invented; and not even 
the genius of a Langley or a Wright could construct a flying 
machine until the internal-combustion engine had reached its 
proper development. 

At present, and during the last four or five years, inventors 
are and have been unusually active in this line of work, and 
there are several machines which are in the course of construction 
or are being experimented upon with the view of perfecting and 
correcting their mechanical details. The following are descrip- 
tions of some of the more prominent : 



INCIDENTAL UNDERGROUND EQUIPMENT 185 

The tunneling machine which is being developed by Mr. O. 
O. App, of the Terry, Tench and Proctor Tunneling Machine 
Company, consists essentially of a rotating head with four arms, 
each of which carries four specially designed pneumatic hammer 
drills, so arranged that practically the entire face of the tunnel 
is covered at each revolution of the head. The drills carry a 
flat wedge-shaped bit and are arranged so that the action of the 
hammer is stopped automatically whenever the pressure of the 
bit against the rock is less than a predetermined amount, thus 
preventing damage to the drill whenever a tool breaks or a 
crack or seam in the rock is encountered. The drill bits are held 
against the rock at a definite angle, and in their operation they 
chip or flake away the rock instead of attempting to pulverize 
it. The head is provided with a flange and shield so arranged 
that the cuttings are hfted from the bottom of the bore and 
discharged upon a belt conveyer which in turn delivers them 
to the tunnel cars at the rear. Air is suppHed to the drills 
through the center of the rotating shaft which carries the head. 
The entire machine is mounted upon wheels to facihtate its 
movement in the tunnel. 

The Bennett tunneling machine consists of a battery of forty- 
six pneumatic hammer drills mounted in a rectangular head, 
arranged so that it can be given a vertical as well as a transverse 
motion, and thus be able to drill a tunnel of any desired size. 
The head is held rigid while the machines are running, and after 
the face of the tunnel has been drilled full of holes the head is 
backed away from the face and the cellular shell remaining 
between the holes is then broken down with hammers. Experi- 
ments are now being carried on with this type of machine in a 
rock heading near Golden, Colorado. 

The International Tunneling Machine Company's machine 
is manufactured under the Fowler patents, and consists of a 
narrow swinging rectangular cutting head, the full size of the 
tunnel, carrying a battery of forty-one rock drills. These drills 
are so placed as slightly to overlap each other's path as the 
cutting head swings from side to side, by which means the 
entire face is cut away. This permits the continuous operation 



186 MODERN TUNNELING 

of the machine, so long as it is in working order, instead of inter- 
mittent attack as is necessary with the Bennett type of machine. 

A full-sized machine was built in 1909 at the Davis Iron 
Works in Denver, but, aside from some experimental cutting 
on a huge block of concrete, nothing was ever done with it, and 
it is now housed in the shop yard. 

The Karns machine is in principle a large reciprocating rock 
drill with a cutting head the full size of the tunnel. In the 
latest machine this head is six feet in diameter and contains 
forty-one cutter blades made of tool steel, each i inch thick, 
5 inches wide, and of various lengths. Points like saw teeth 
are machined on one edge and the other edge is fastened in the 
face of the head. The reciprocating parts of the machine weigh 
seven and a half tons and make about 140 strokes per minute 
of seven inches each. The head is rotated sKghtly on each 
return stroke. The machine uses 2,000 cubic feet of air per 
minute. One runner, one helper, two muckers, one engineer, 
and a fireman are needed to run the machine, and a blacksmith 
and helper are required, one shift in three. 

The Retallack & Redfield tunnehng machine, now under con- 
struction at the Vulcan Iron Works in Denver, is intended to bore 
an eight-foot cyHndrical tunnel. A machine of this size carries 
twenty-eight percussion drills, symmetrically arranged on a 
revolving head, each drill having 3 >^ -inch pistons, carrying i%- 
inch steel bits with the regular cruciform cutting face 6 inches 
in diameter, so shaped that the twenty-eight drills in one revolu- 
tion cover and cut away the entire face. Behind the drills, 
immediately surrounding the cylinders which actuate them, is a 
steel tube about 6 feet in length and 7 feet 5 inches in diameter, 
or 7 inches less than the bore. The outside of this shell is sur- 
rounded by three-inch flanges arranged as a worm conveyer 
to force the cuttings back from the face. The rear end of this 
tube carries two small, pivoted, self-loading buckets or skips, 
which are filled at the lower part of their travel and emptied 
at the upper where they are inverted by a trip, discharging 
their contents on an endless rubber belt which carries the cuttings 
rearward and drops them into a car. 



INCIDENTAL UNDERGROUND EQUIPMENT 187 

The Sigafoos tunneling machine is practically a horizontal 
stamp mill, the stamps being thrown forward by coiled springs 
and drawn back by a revolving cam. In practice ten heads are 
employed and the stamps, instead of being flat, carry an equip- 
ment of hardened steel faces designed to operate with as great a 
cutting effect as possible. To prevent the steel from heating 
and losing its temper, the entire face is sprayed with water, 
which not only lowers the temperature, but allays the dust 
and assists materially in removing the cuttings. 

Although a number of experimental machines have been 
built, all of the details of construction are not yet perfected. 
The American Rotary Tunneling Machine Co. is now ex- 
perimenting with an eight-foot machine near Georgetown, 
Colorado. 

One of the great obstacles encountered by legitimate in- 
vestigators in this field has been the difficulty of obtaining funds; 
for with the tunneling machine as well as with any other new 
and complicated machine built to operate under difficulties 
and strains which cannot be measured in advance, costly ex- 
perimental work is necessary in its development and process of 
perfection. It must be remembered that machines of the size 
and strength to cut the entire face of the tunnel in a single opera- 
tion are of necessity costly, and their maintenance during the 
trial stages is extremely expensive. For this reason, success 
can hardly be hoped for unless the inventor, or the company 
back of him, is in a position to command very considerable 
amounts of money. But the failure of one badly designed and 
inadequately financed machine after another, and the sus- 
picions which have been aroused in the minds of possible in- 
vestors by the untruthful and flamboyant ''literature" which 
has been issued by too many alleged tunnel-machine companies 
in their efforts to "work the public," have caused most people 
to look upon machines of this kind with extreme distrust, much 
of which is indeed just, for even a casual scrutiny of the claims 
of many of these concerns shows clearly that they are in reality 
fit subjects for investigation by the postal authorities. 

The following paragraphs contain a list of patents issued 



188 MODERN TUNNELING 

in the United States for tunneling machines in hard rock, ar- 
ranged in the order of seniority. With each patent is given a 
condensed description of the "objects of the invention" or the 
"patent claim." At the time the examination was made the 
Patent Ofhce was rearranging this class of inventions, and 
therefore, although every effort was made to have the Ust com- 
plete, it is possible that one or two inventions may not have been 
included in it. 

List of Tunneling Machine Patents 

E. Talbot Stone-Boring Machine, U. S. Patent No. 9,774, 
patented June 7, 1853. 

Description not available, but Patent Office drawings 
show a machine adapted to boring a cylindrical tunnel with 
rotating disk cutters. Two pairs of disks are used, carried 
on a revolving head supported by a large hollow horizontal 
shaft. This head is intended to be slowly revolved by a 
worm-driven spur gear, and through the hollow shaft is 
carried a jointed connecting rod by means of which the 
cutting disks are traversed across the face of the revolving 
head so that all portions of the heading are subject to the 
cutting action of the disks. The machine is quite crude 
in its design, and it is plainly apparent that it had not 
passed the experimental stage. 

Charles Wilson, Springfield, Massachusetts, U. S. Patent 
No. 14,483, patented March 18, 1856. 

Claims: Invention "consists in so arranging, constructing, 
and fitting the parts of a revolving cutter wheel that the 
cutters are gradually forced forward with a very slow motion, 
while the wheel carrying the rolling disks, or cutters, receives 
a compound motion, the one motion a revolution on its 
shaft, which is at right angles to the axis of the tunnel being 
bored, and the other motion a gradual rotation of said 
cutter-wheel and parts carrying the same on the fine of axis 
or general direction of said tunnel. These two motions, in 
addition to the very slow forward feeding motion produced 



INCIDENTAL UNDERGROUND EQUIPMENT 189 

by the rolling cutters, causes the gradual removal of the rock, 
or other substance, at the semi-spherical end of the tunnel.'' 
Charles Wilson, Springfield, Massachusetts, U. S. Patent 
No. 17,650, patented June 23, 1857. 

"The plan adopted in this method of tunneling is to 
bore a single ring and a central hole. By means of a charge 
of gunpowder, afterward placed in the central hole and ex- 
ploded, the rock intervening between the central hole and 
circular groove is detached." 

Claim: "Forming grooves in stone, or other mineral 
substances, by means of rolling disk cutters on axes set in 
alternate directions and arranging a series of rolUng disk 
cutters revolving in such a manner as to cut a deep annular 
groove into the rock." 
F. E. B. Beaumont, England (English Patent No. 1,904), 
patented July 30, 1864. 

"Gang of cutters; supplementary valve; tappet and 
annular projection; hand feed; rotation automatic by worm 
and feather." 
Thales Lindsley, Rock Island, Illinois, U. S. Patent No. 55,514, 
patented June 12, 1866. 

Machine devised, "first, to cut circular concentric channels 
in vertical planes of rock and thus form circular concentric 
rings in the heading; second, to disrupt these concentric 
rings of rock and thus prepare them for removal; third, to 
detach the fragments of the disrupted rings and deUver them 
for transportation," etc. 
Edward M. Troth, New York, New York, U. S. Patent No. 
66,422, patented July 2, 1867. 

A reciprocating head carrying a number of drills arranged 
to vary the stroke. This head turns slowly, cutting a 
number of concentric grooves in the face. The rings of rock 
remaining behind are broken off by wedges. 
Richard C. M. Lovell, Covington, Kentucky, U. S. Patent 
No. 67,323, patented July 30, 1867. 

This is a chipping machine, the chisels being operated 
alternately by their respective engines, the leading chisel 



190 MODERN TUNNELING 

cutting half the depth and the following one completing 
the cut, and being reversed and changed in cutting back; 
.the motor is operated by either steam or compressed air 
conducted to the engine by pipes from the exterior of the 
shaft or drift, etc. 

John D. Brunton, London, England, U. S. Patent No. 80,056, 
patented July 21, 1868. 

Patent claim: ''The use of an apparatus for excavating 
tunnels, galleries, or adits, wherein one or more cutting 
disks are caused to revolve on their axis, or axes, such 
axis, or axes, revolving around a center which also revolves 
around another fixed center." 

Edward Alfred Cooper, Westminster, England (English patent 
No. 1,612), patented June 20, 1871. 

Claim: ''The cutting of grooves, or chases, in stone or 
rock by the action of a series of chisels or jumpers, each 
worked by compressed air or steam acting in a separate 
cyHnder and moved along its groove or chase, and all«advance 
as the grooves or chases are deepened." 

Allexey W. Von Schmidt, San Francisco, California, U. S. 
Patent No. 127,125, patented May 21, 1872. 

Claim: "In combination with a cylindrical drumhead 
arranged to rotate on its axis, a series of rotary diamond- 
pointed drills mounted on the periphery of the drumhead." 
By this means an annular groove the size of the tunnel is 
cut in the rock to a depth of about two feet, when the 
machine is backed out and the central core removed by 
blasting. These diamond-pointed drills are cooled by a 
stream of water sprayed into the annular groove. 

Frederick Bernard Doering, Trefriw, North Wales, England, 
Enghsh Patent No. 4,160, September 27, 1881. 

"A tunneling machine on which is mounted by means of 
brackets, or otherwise, a series of rock-boring machines 
or drills, say four, more or less, around a central boring 
machine or drill, each carried at the end of an arm, prefer- 
ably consisting of a strong steel tube. This steel tube, 
which is accurately turned on its outer face, is supported 



INCIDENTAL UNDERGROUND EQUIPMENT 191 

by one, two, or more accurately bored castings which are 
carried on a strong framework mounted on wheels. The 
boring machines or drills may be fitted with cross-heads 
carrying chisels, or they may have a single chisel attached 
with or without a cross-head. The drills strike and rotate 
a portion of the circle with each stroke in the usual manner.'* 

Thomas English, Hawley, Kent, England, U. S. Patent No. 
307,278, patented October 28, 1884. 

*' Invention relates to a machine for boring a circular 
tunnel by means of a boring head which consists of a strong 
boss having two arms projecting radially from it, each arm 
having a number of cutters fixed in front of it, each cutter 
being a bevel-edge disk fixed to the holder so that it can 
be turned partly around when one part becomes blunted. 
Jets of water from small nozzles play on the cutters to 
prevent them from heating." 

Henry S. Craven, Irvington, New York, U. S. Patent No. 
307,379, patented October 28, 1884. 

This patent ''relates to that class of machines which 
employ a drill or combination of drills constructed to cut 
or bore an annular groove the full size of the contemplated 
tunnel, leaving a cylindrical mass of rock at the end of the 
bore to be blasted out by a charge of explosives introduced 
in the central hole." 

Robert Dalzell, Waddington, New York, U. S. Patent No. 
332,592, patented December 15, 1885. 

Claims: ''In a rock-drilling machine the combination 
of a suitable frame carrying a rotating or oscillating tubular 
shaft having near its forward end a series of laterally radiat- 
ing arms, having adjustably screwed to their outer ends 
one or more reciprocating or rotary drills with mechanism 
for operating the same both simultaneously or separately." 

F. 0. Brown, New York, New York, U. S. Patent No. 340,759, 
patented April 27, 1886. 

Patent claims: "A shell made in the shape and size of 
the required tunnel, provided with an air-tight cross parti- 
tion having manholes closed by plates in the tube, a 



192 MODERN TUNNELING 

central worm-boring mechanism, and a steam pipe passing 
through the airtight partition in the tube." 
Reginald Stanley, Nuneaton, England, U. S. Patent No. 
414,893, patented November 12, 1889. 

Claim: ''In a tunneling machine the combination of a 
frame carried on central tandem wheels working on the 
floor of the tunnel, a central threaded shaft carried by said 
frame and driving wheel working on said shaft, radial arms 
and horizontal arms on one end of said shaft and provided 
with cutters and scrapers depended for forming an annular 
groove around the face of the tunnel," etc. 

Reginald Stanley afterward devised numerous improve- 
ments on this machine which were patented June 14, 1892; 
May 9, 1893; August 29, 1893; August 11, 1894; and Febru- 
ary 16, 1897. 
Frederick Dunschede, Essenberg, Germany, U. S. Patent 
No. 507,891, patented October 31, 1893. 

''Invention consists of an apparatus by means of which 
an annular groove and a central blasting hole are bored into 
the rock so that, on inserting into said central hole an 
explosive and exploding the same therein, the rock or other 
material forming the core between the central blasting 
hole and the circumferential cut will be smashed and 
blown away." 
Jonas L. Mitchell, Chicago, Illinois, U. S. Patent No. 537,899, 
patented April 23, 1895. 

Claim: "In a tunneling machine, the combination of a 
tunnel-forming cutter consisting of a tubular cutter head, 
a main frame having guides therein, and of a diameter 
^ adequate to enter the tunnel formed by the cutter, a carriage 
sliding in said guides and lying in the transverse planes 
of the bed," etc. 
Harry Byrne, Chicago, Illinois, U. S. Patent No. 545,675, 
patented Spetember 3, 1895. 

Patent claims: "In a rock- tunneling apparatus, the 
combination of an upright supporting frame, having a 
marginal frame corresponding with that of the tunnel and a 



INCIDENTAL UNDERGROUND EQUIPMENT 193 

series of traveling percussion channeling machines arranged 
to travel on the outer surface of said frame; a flexible 
connection attaching the entire series of machines together 
and causing same to travel in unison, and means for operating 
said flexible connection." 

Archie LE Bailey, Philipsburg, Pennsylvania, U. S. Patent 
No. 640,621, patented January 2, 1900. 

Patent claims: ''In a mining machine, the combination 
with a bed, the carriage, two reciprocating cutters, each 
forming a separate curve, and means for simultaneously 
reciprocating said cutters in opposite directions, whereby 
they balance the machine laterally, of a drill mounted on 
each side of the carriage and forming an aperture at the 
end of the kerf." 

John E. Ennis, Chicago, IlKnois, U. S. Patent No. 690,137, 
patented December 31, 1901. 

Claims: "A tunneling machine having a digger mechanism, 
including a plow movable in a circular sweep, means for 
imparting said sweep movement to the plow, and simul- 
taneously forcing forward in a spiral direction, and means 
for automatically shifting movements of the plow and 
causing it to travel from the perimeter of the machine 
inward, or from the axis of the machine outward, during 
its sweep movement." 

Pedro Unanue, City of Mexico, Mexico, U. S. Patent No. 
732,326, patented June 30, 1903. 

Claims: "In a tunneling machine, the combination of 
a ram-head provided with a series of rammers having their 
rods inclined to the ram-head in and toward the direction 
of revolution of the ram-head, together with an incHnation 
from the axis of revolution of the ram-head, and means for 
rotating and feeding said ram-head," etc. 

John Prue Karns, Cripple Creek, Colorado, U. S. Patent No. 
744,763, patented November 24, 1903. 

Claims: "The combination with a tunneling machine of 
a revoluble drill support comprising a pluraHty of ring 
and spoke members, each having grooved forward faces, 



194 MODERN TUNNELING 

drills, or cutters, having their base portions adapted to said 
grooves, each of the drills or cutters having a rearwardly 
, projecting stem extending through an opening in the support, 
and means for locking said stems to said support." 

Other patents issued to Mr. Karns on this machine are 
as follows: 

No. 957,687, May 10, 1910, for improvements in machine 
structure, particularly for the front bearing of the cutter- 
head shaft. 

No. 977,955, December 6, 1910, for improvements in the 
cutter-head tool-carrying spider. 

No. 1,023,654, April 16, 1912, improvements on the 
structural form and mechanical arrangement of said machine. 
Chester T. Drake, Chicago, Illinois, U. S. Patent No. 747,869, 
patented December 22, 1903. 

Claims: ''In an excavating machine, the combination of 
a shaft provided on its end with a cutter, mechanism for 
revolving the shaft, mechanism for giving shaft and cutter 
an orbital revolution, and adjustable mechanism for varying 
orbit described." 
Alva D. Lee, of Brookline, and Francis J. E. Nelson, Jr., of 
East Boston, Massachusetts, U. S. Patent No. 874,603, 
patented December 24, 1907. 

Claim: "In a rock-drilling machine, the combination ' 
of an annular face plate provided with a pluraHty of de- 
pressions in its face, means for rotating said plate and a 
plurality of cutters secured in said depressions, with their 
axes radial to the axis of said plate and at different dis- 
tances from said center, thereby effecting in the revolution of 
said plate a cutting from the central opening to the outer 
periphery of said plate," etc. 
Silas A. Knowles and Walter E. Carr, Idaho Springs, 
Colorado, U. S. Patent No. 875,082, patented December 31, 
1907. 

Claim: "In a tunneling machine, a narrow rectangular 
reciprocating cutter head of the full height of the tunnel 
to be. driven, provided with vertically and parallely ar- 



I 



INCIDENTAL UNDERGROUND EQUIPMENT 195 

ranged rows of chisel-shaped drill bits having angular 
bases, means for securing said drill bits to said cutter 
head, said cutter head having slideway slots therethrough, 
a supporting guide arm having forward terminal arms 
which project into sHdeway slots on which said cutter head 
is reciprocally mounted," etc. 

William J. Hammond, Jr., Pittsburgh, Pennsylvania, U. S. 
Patent No. 885,044, patented April 21, 1908. 

Claim: ''In a tunneling machine, a rotary head having 
a series of diametrically arranged reciprocating hammers 
and separated from each other by distances slightly less 
than the hammers, whereby the entire breast of the tunnel 
may be disintegrated by the rotation of the head and the 
reciprocation of the hammers." 

George Allen Fowler, Georgetown, Colorado, U. S. Patent 
No. 891,473, patented June 23, 1908. 

"Invention is directed to the production of a pneumatic 
mining machine for a plurahty of thrust-actuated drills 
adapted particularly to tunnel or driving operations in 
which the drills are carried by a pivoted block, which, in 
its cutting operations, is automatically caused to travel 
back and forth, reducing the wall of the breast to an arc 
of a circle to give clearance to the sides of the machine." 

Olan S. Proctor, Denver, Colorado, U. S. Patent No. 900,950, 
patented October 13, 1908. Assigned to the Terry, Tench 
& Proctor Tunneling Machine Company. 

Claim: "In a rotary tunneling machine, the combination 
of a supporting frame, a tubular shaft revolubly mounted 
on said frame, a rotary cutter head secured to one end of 
said tubular shaft, a plurality of operative rock-drilling 
engines arranged to cut the breast area of a circular tunnel, 
said cutter head having ports leading from said tubular 
shaft to said rock-drilling engines, means, including a 
motor, for rotating said tubular shaft and cutter head, 
means for connecting the opposite end of said tubular 
shaft to a supply of suitable drilling engine actuating fluid, 
a muck-catching cylinder on said supporting frame sur- 



/ 



196 MODERN TUNNELING 

rounding said cutter head, and means for conveying the 
muck from said cutter head and cyhnder to the opposite 
end of said supporting frame from said cutter head." 

Russell B. Sigafoos, Denver, Colorado, U. S. Patent No. 
901,392, patented October 20, 1908. 

''The objects of this invention are: First, to provide 
a rotary tunnel machine adapted to automatically feed 
into the breast of a tunnel as fast as it cuts into rock, and 
to automatically feed forward and backward. Second, 
to equip it with a pluraHty of reciprocating cutter heads, 
each provided with a plurality of independent rock-cutting 
lips. Third, to provide a plurality of reciprocating rotary 
cutter heads adapted to strike spirally twisting blows. 
Fourth, to provide discharge jets of water throughout the 
circumference of the rock-cutting area. Fifth, to provide 
the machine with a plurality of independent rotating and 
spirally striking cutter heads arranged and adapted to 
permit any one or predetermined number of said cutter 
heads to be adjusted to strike blows at differential force. 
Sixth, to provide an automatic adjustable feeding 
mechanism that will feed the machine forward in any 
predetermined curved path as it cuts its way into the 
rock." 

Joseph Retallack, Denver, Colorado, U. S. Patent No. 906,741, 
patented December 15, 1908. 

This machine is especially designed for driving tunnels 
or drifts through rock, and it comprises, in general, "a 
revoluble tool head which may be idly rotated or fed forward 
or backward at pleasure. The head carries a large number 
of independently actuated rock drills which attack the face 
of the rock as the head is rotated. The head is carried by 
a threaded shaft that is hollow from end to end and serves 
as a duct for the passage of the air or other fluid to actuate 
the drills." Provision is also made for introducing water 
at the drilling point and for automatically gathering up and 
conveying away the fragments of rock as the tunneling 
operation proceeds. 



INCIDENTAL UNDERGROUND EQUIPMENT 197 

Charles A. Case, New York, New York, U. S. Patent No. 
910,500, patented June 28, 1909. 

''This invention relates to means for disintegrating rock 
and other materials by suddenly changing their temper- 
ature, and then by concussion, hammering, or rasping, 
effecting their disintegration." 

Edward T. Terry, New York, New York, U. S. Patent No. 
917,974, patented April 13, 1909. 

"The primary object of this machine is to cut a tunnel 
through rock without the necessity of blasting." . . . 
"The drill head consists of nine gangs of drills of such size 
and location that in their rotary motion they cover substan- 
tially the whole face of the tunnel, while the cutting action 
is produced by a rapid reciprocation of the separate heads." 

Louis Franklin Sleade, Denver, Colorado, U. S. Patent No. 
945,623, patented January 4, 1910. 

Claim: "A tunneling machine comprising a revoluble 
cutter head, an electric motor for rotating said cutter 
head, an internal combustion engine for maintaining a 
reciprocating motion of the said cutter head in a forward 
direction, and means for connecting said electric motor 
with said internal combustion engine, imparting a returning 
movement to the cutter head." 

George R. Bennett, Denver, Colorado, U. S. Patent No. 
958,952, patented May 24, 1910. 

Claim: "A tunneling machine comprising, in combination 
with a suitable support, a battery of rock drills, means for 
presenting said battery to a working face, means for pro- 
jecting said drills of said battery in said face, and means 
for automatically moving said battery laterally after each 
projection of said drills. 

"A tunneling machine comprising, in combination with a 
suitable support, a battery of rock drills, means for im- 
parting a series of rectilinear movements to said battery, 
and means for automatically performing said movements, 
in progressive cycles, each cycle comprising a longitudinal, 
lateral, and vertical movement." 



198 MODERN TUNNELING 

William R. Collins, Georgetown, Colorado, U. S. Patent 

No. 973,107, patented October 18, 1910. 

"Invention provides a machine having a cutting head 
which will leave an uncut rock core, thereby saving a certain 
amount of expensive rock drilling, and further to provide 
an improved arrangement of chipping or cutting drills 
V whereby the recoil of the drills will be counteracted and 

the cutting head balanced." 

On August 8, 191 1, Mr. Collins obtained U. S. Patent 
No. 1,000,075 for certain mechanical improvements on 
this machine. 
Aron G. Seberg and Edwin G. Seberg, Racine, Wisconsin, 
U. S. Patent No. 976,703, patented November 22, 1910. 

Claim: ''In a drilling machine, the combination with a 
wheel, of shields yieldingly mounted in said wheel, drills 
slidably mounted in said shields, means to force said drills 
beyond the outer ends of said shields, and means to rotate 
said wheel. 

''In a drilling machine, the combination with a rotating 
sleeve, of a wheel for said sleeve adapted to rotate there- 
with, a supporting axle around which said wheel revolves, 
means to rotate said wheel, a plurality of drills carried 
by said wheel, and rotating means adapted to force said 
drills outwardly and enter the same into an object." 
Franklin M. Iler, Denver, Colorado, U. S. Patent No. 986,293, 
patented March 7, 1911. 

Claim: "In a rock-drilHng machine, the combination 
with a suitable frame, of a hollow rotatable shaft, carried 
by said frame, divergent, rigid, hollow arm constituting a 
continuation of said hollow shaft and projecting therefrom 
at an angle, means for supporting fluid-operated drills by 
said arms in various adjusted positions at different points, 
and means for connecting the inlet ports of said drills with 
the interior of said arms." 

Mr. Iler has also patented, for use with his machine, a 
special drill bit which consists of a hollow tube about 7 inches 
in length, 3^ inches external diameter, and i^ inches 



INCIDENTAL UNDERGROUND EQUIPMENT 199 

internal diameter. This tube is of cast iron or soft steel, and 
in it are embedded a number of rods about j^ inch in diam- 
eter of exceedingly hard alloy steel. The soft material 
wears away much more rapidly than the hard, thus forming 
a chipping tool which can be used without sharpening until 
it is worn out. 
George A. Fowler, Denver, Colorado, U. S. Patent No. 996,842, 
patented July 4, 191 1. 

Invention ''provides a suitable frame mounted on wheels, 
said frame being provided at its forward end with a drill 
head provided with a plurality of fluid-operated drills, 
said head being pivotally mounted on the frame and adapted 
to swing from side to side in the arc of a circle, upon a 
vertical axis, means being provided for admitting fluid 
under pressure to said drills, and for automatically swinging 
said head from side to side and for manually moving said 
machine forward against the breast of the tunnel." 
Robert Temple, Denver, Colorado, U. S. Patent No. 1,001,903, 
patented August 29, 191 1. 

''Invention provides a machine for cutting tunnels 
through rock or ether materials, the cutter of which will 
be reciprocating and simultaneously moved transversely 
to its direction of reciprocation, thereby cutting a tunnel 
of greater cross-section than the machine." 

Claim: "In a rock-cutting apparatus, the combination 
with a transversely extending head, of a plurality of cutters 
mounted thereon, means for reciprocating said head, and 
means for simultaneously mo\ing the same in complete 
cycles over a substantially circular path adjacent to the 
surface worked upon and eccentric to the said head." 
John Nels Back, Seattle, Washington, U. S. Patent No. 
1,011,712, patented December 12, 191 1. 

Claim: "A tunnel-excavating machine comprising an 
outer frame, traction wheels under said outer frame, an 
inner frame movable with relation to said outer frame, a 
head beam, a carrier slidably mounted upon said head 
beam, a shovel mounted in said carrier, means for sliding the 



200 MODERN TUNNELING 

carrier, means for moving said inner frame, and toggle- 
joint braces to prevent movement of said outer 
frame." 

Edward O'Toole, Gary, West Virginia, U. S. Patent No. 
1,011,955, patented December 19, 191 1. 

Claim: ''In an excavating machine, the combination of 
a frame, a pair of rotary pick-armed cutter heads mounted 
on parallel shafts therein, and geared to rotate in unison 
from a common source of power, said frame movable upon 
a bed-plate, and in movement causing the shafts of said 
cutter heads to move transversely in their common plane, 
said bed-plate provided with a passage for excavated 
material, and with an intake extending beneath the path 
of movement of said cutter heads." 

Henry F. Sutton, Salt Lake City, Utah, U. S. Patent No. 
1,025,029, patented April 30, 191 2. 

''Object of invention is to subject the rock alternately 
to the action of opposite extremes of temperature, it having 
been found that when rock is first heated and then sud- 
denly chilled it becomes softened or partially disintegrated 
so as to be easily removed by hand or by pneumatic tools 
or the like." 

Claim: "Apparatus for tunneling rock, including a 
hollow head having a mixing chamber therein, said head 
having a working face formed with a plurality of minute 
apertures, means for pivotally supporting the head close 
to the surface to be acted upon, means for directing fuel 
into the head, valves for controlling the passage of fuel 
through said means, and means for directing air under 
pressure into the head." 

Adolph F. Walther, Oakland, California, U. S. Patent No. 
1,026,335, patented May 14, 1912. 

Claim: "A tunneling apparatus comprising a plurahty 
of main frames, detachable braced supports for holding said 
frames in a tunnel, a frame movable longitudinally in said 
plurality of frames, a rotary shaft and head mounted in 
said frame, radial bars provided with cutters mounted 



INCIDENTAL UNDERGROUND EQUIPMENT 201 

on said rotary head, and mechanism for operating said 
rotary head and cutter bars." 

L. H. Rogers, New York, New York, U. S. Patent No. 1,039,809, 
patented October i, 191 2. 

Claim: ^'The combination of a central frame, a hollow 
shaft journaled in the frame, means to conduct a fluid to 
the interior of said shaft, a front head fastened to said 
shaft, grinding wheels journaled on said head, motors 
connected to the wheels carried on the head, means to 
conduct the fluid from said shaft to said motors, a rear 
frame sUdably connected to the shaft, a cylinder encircling 
said shaft and fastened to the rear frame, a piston in the 
cyHnder connected to said shaft, and means to lead a 
compressed fluid on either side of the piston." 

W. F. WiTTiCH, Erie, Pennsylvania, U. S. Patent No. 1,043,185, 
patented November 5, 191 2. 

Invention utilizes ''a rotating head in which is mounted 
a series of cutters actuated, preferably, independent of 
the head, so that the head may be advanced slowly or 
rapidly, depending on the material being operated upon, 
and the cutters given a speed which will assure the greatest 
efficiency. In the preferred form of the machine, also, 
the head is separated from the driving parts of the mechan- 
isms, so that the machine may be utilized and rapidly 
advanced where there is considerable leakage through the 
walls. The invention also contemplates a suitable mount- 
ing, or frame, for carrying the working parts, taking away 
the muck, and driving the several parts." 

ILLUMINATION 

With few exceptions, illumination for tunnels and adits in 
the United States at the present time is furnished by electricity, 
acetylene gas, or candles. The smoky open-flame miner's 
oil-lamp is occasionally used in tunnels situated in the 
coal-mining districts, and, of course, under conditions which 
prohibit the use of an open flame, safety lamps must be em- 
ployed. When acetylene gas is employed it is usually generated 



202 



MODERN TUNNELING 



in portable lamps, but during the work on the water conduit 
for Washington, D. C, in 1899, this gas was manufactured at 
a plant on the surface and carried by pipes underground where 
it was burned in jets at regular intervals. Coal gas was simi- 
larly employed at the Mt. Cenis tunnel, which was started in 
1857 ^^^ opened for traffic in 1872. The following table, how- 
ever, shows the present practice with regard to means of illumi- 
nation. 



MEANS OF ILLUMINATION AT VARIOUS TUNNELS 



Tunnels 


Illumination 


Buffalo Water 


Electric lamps. 

Acetylene lamps and candles. 

Eleotric lamps at intervals and usually a cluster 

of lamps in the headings. 
Acetylene lamps. 
Electric lamps (16 c.p.) every 75 feet and one 

32 c.p. in heading 
Candles, 


Carter 


Catskill Aqueduct 

Central ... 


Fort Williams . . 


Gold Links 


Gunnison 


Electric lamps. Cluster in heading and candles. 

Electric lamps. 

Acetylene lamps for drillers, candles for muckers. 

Miners' oil lamps and safety lamps. 

Electric lamps and candles. 

Acetylene lamps. 

Acetylene lamps. 

Electric lamps every 200 feet, cluster in head- 
ing, candles. 

Electric lamps at stations, acetylene lamps in 
heading. 

Electric lamps every 75 feet, cluster in heading. 

Candles. 


Joker 


Laramie-Poudre 


Lausanne 


Los Angeles Aqueduct .... 
Lucania. 


Marshall-Russell 


Mission 

Newhouse 


Nisqually 


Ophelia 


Raymond 

Rawley 


Electric lamps every 200 feet, cluster in heading. 

Acetylene lamps. 

Electric lamps. 

Electric lamps every 200 feet and candles. 

Acetylene lamps. 

Electric lamps in heading, candles. 

Electric lamps every 135 feet, cluster in heading. 

Electric lamp at switch, acetylene lamps in 

heading. 
Electric lamps. 


Roosevelt 


Siwatch 

Snake Creek. 


Stilwell 


Strawberry 

Utah Metals 


Yak 





Neither candles nor the open-flame oil lamp can be recom- 
mended as a means of hghting a tunnel or adit during con- 
struction. Practically everything that can be said in their favor 
is that they require a much smaller initial outlay than electricity 



INCIDENTAL UNDERGROUND EQUIPMENT 203 

or acetylene, yet they are more expensive per unit of light than 
either acetylene or electricity, consume a greater amount of 
oxygen, and give off a correspondingly greater amount of noxious 
gases. Candles not only do not give enough light, but what they 
do supply is flickering and unsteady unless there are no drafts, 
and since they are quickly extinguished by the exhaust blasts 
from air drills they cannot be placed to light properly the work 
of the drillers; hence the efficiency of a high-priced drillman 
is greatly reduced. Candles are often wasted or dropped into 
the muck-pile, an item of loss which may amount to a consider- 
able sum in the long run. The open-flame oil lamp cannot be 
prevented from giving off soot and smoke which obscure and dim 
the light thrown on the work, while the soot collecting in the 
miner's throat and lungs irritates the mucous membranes and 
renders them easily susceptible to disease. 

Electric incandescent lamps possess a number of advantages 
for tunnel work. They give a brilliant and steady Hght — one 
that is not affected by drafts and neither pollutes the air with 
soot nor vitiates it by consuming the oxygen. By combining 
several of them in a cluster, plenty of light in the heading is 
obtained for the drillers and shovelers, tending toward efficiency. 
To offset this advantage, however, the fact remains that unless 
they are used in connection with electric locomotives, drills, 
or similar machinery, the cost of lamp installation is almost 
prohibitive; even with the electric appliances in use the extra 
wiring and the lamps themselves are expensive, while the latter 
are subject to considerable loss through breakage. Electric 
lights are also at a disadvantage because they are not easily 
portable and the removal and replacement of bulbs and wires 
in the heading before and after blasting compHcate an already 
involved situation. Moreover, this means of illmnination is 
uncertain, especially in wet tunnels, because the chance oc- 
currence of a short circuit through moisture, accident, or care- 
lessness throws the entire work in darkness, and if other means 
of Hghting are not at hand, stops all work until the trouble 
can be remedied. Again, whereas the use of electricity under 
ground is always attended with some danger, this is especially 



204 MODERN TUNNELING 

true in the case of lighting appKances; the supposition is that 
the wires are protected, but the rough usage to which they are 
subjected soon destroys insulation, rendering persons who 
handle them (as they must do frequently) subject to severe 
shock. 

One is tempted to say that the ideal means of tunnel illu- 
mination is found in the portable acetylene lamp, combining 
as it does the advantages of other illuminants while avoiding 
most of their defects. It may be obtained on the market 
to-day in a number of different designs and sizes adapted for 
practically every kind of work; the one most generally observed 
at the tunnels visited was about the size of an ordinary can 
of fruit and capable of burning for from eight to ten hours on one 
charge of carbide and water. Although too large for use on a 
cap, it was provided with a hook so that it could be suspended 
from any convenient place. Lamps suitable for wearing on an 
ordinary miner's cap are obtainable and these lights will burn 
for two or three hours without recharging, an operation which 
can be done easily in two or three minutes. The initial ex- 
pense of an acetylene lamp is not high and it furnishes the 
brightest known artificial light used for underground work, 
with the possible exception of the electric arc, consuming the 
while only one-fifth as much oxygen as candles. The lamps are 
ordinarily provided with a reflector, which not only concentrates 
the light upon the work where it is needed, but shields the flame 
from drafts so that it will burn steadily unless placed directly 
in front of the exhaust from an air drill. Extensive use in 
some of the larger mining companies in this country has shown 
that the cost of the carbide is much less than either oil or candles 
and the use of acetylene lamps practically cuts the cost of light 
in half. At the Saginaw mine, Menominee Range, Michigan, 
the cost is reported as only two cents per shift of ten hours. 
Such lamps require practically no attention, are completely 
portable, and are not subject to breakage as are incandescent 
lamps. By giving the workman plenty of light his efliciency 
is not only increased, but he is better able to see and guard 
against the dangers of underground work, such as an insecure 



INCIDENTAL UNDERGROUND EQUIPMENT 205 

roof, an unexploded stick of dynamite in the muck-pile, or any 
other of the many dangers to which he is at all times exposed. 

TELEPHONES 

Although it has been repeatedly stated in newspapers, 
engineering periodicals, and even by State legislatures, that 
every mine should be provided with a telephone system, the 
importance of telephones in tunnel work cannot be too often 
reiterated, not alone because of the greater safety they insure, 
but on the ground of efficiency and economy as well. The 
sources of accident in tunnel work are too numerous to mention 
— falls of roof, caves, premature or delayed explosions, water, 
and noxious gases being some of the more common. When an 
accident occurs in a tunnel that is equipped with a telephone 
system, not only can assistance be summoned quickly, but 
provision can be made beforehand for the care of injured men 
when they reach the surface; if professional help can be sum- 
moned and due preparation made while the men are still on the 
way from the /^ea^/m^, invaluable time is saved; for there have been, 
and doubtless will be in the future, many such instances where 
prompt medical attention has decided the question of life or 
death. Then, too, failure to obtain a proper round of holes 
in the given time, difficulty in blasting them to the full depth, 
or any of the many problems that commonly arise in tunnel- 
driving, call for a decision on the part of the foreman as to the 
method of procedure. Ordinarily the man entrusted with this 
position is capable of meeting such conditions as they arise, 
but it stands to reason that the work of the shift will be more 
efficient if the foreman can be in touch constantly with the 
mine superintendent and when in doubt receive suggestions and 
advice from the more experienced man's better judgment. 
Delay can be avoided in good part if the tunnel is equipped 
with a telephone, because the necessity that involves sending 
for fresh materials, tools, powder, etc., can either be foreseen 
and proxdded for promptly from the outside without the loss of 
a man from the heading crew, or when unexpected emergencies 
arise, only half the usual time is necessary to obtain the needed 



206 MODERN TUNNELING 

supplies. It does not require many suspensions of work by the 
men in the heading, waiting while one of their number walks to 
the portal and back, to pay for the entire installation of such 
equipment. Causes of accident and delay cannot always be 
foreseen, it is true, but they can bo met promptly and further 
damage to men and property can be prevented by the use of the 
telephone; that these advantages are appreciated is shown by 
the fact that a majority of the tunnels and adits examined 
in the field were so equipped. 

The type of telephone-equipment should be carefully chosen, 
because every telephone is not suited for underground use. 
For use in tunnels it must be water-proof, dust-proof, and, since 
to be useful it must be placed as near the heading as possible, 
it must be designed to withstand the frequently recurring con- 
cussions of blasting. The most successful types of mine tele- 
phones meet these conditions by placing the mechanism in a 
heavy metal casing, in such a way that the essential parts shall 
be instantly accessible upon opening the outer door, but shall be 
tightly sealed when it is closed. The more delicate mechanism 
is guarded further by an inner door, also of iron, and the wires 
are protected so that water cannot enter the casing. The bells 
must necessarily be placed outside, but they are protected by a 
metal hood, which, however, does not prevent their being heard 
for a considerable distance. 

The telephone line for tunnel work is somewhat simpler than 
a similar line on the surface, because no poles are required and the 
wires can be strung from ordinary glass or china insulators 
fastened to plugs in the roof or to light cross-timbers. Common 
bare iron wire can be used, but much better results are obtain- 
able where rubber-covered wire is employed, and for the same 
reason a full metaUic circuit is desirable, although the telephone 
may be operated with only one wire by using a ground connec- 
tion for the return. But since the usefulness of a telephone 
system is measured entirely by its rehabiHty, the best is in the 
end by far the cheapest. 

It is not desirable to place the telephone nearer the heading 
than several hundred feet, not only because of the concussion, 



INCIDENTAL UNDERGROUND EQUIPMENT 207 

but also because of the noise. While this arrangement is con- 
venient for any one in the tunnel desiring to call up the office, 
it makes it more difficult and sometimes even impossible to secure 
any response to a call originating on the surface. To obviate 
this difficulty, the use of an extension loud-ringing call-bell 
is recommended, which, if placed behind a jutting rock or in some 
similar protected position, apprises the foreman at the heading 
instantly of any call at the telephone. Such a bell should be 
connected with the telephone circuit by a flexible insulated 
cable mounted upon a reel in such a way that the bell may be 
advanced regularly to keep pace with the tunnel progress and 
need never be further than two hundred feet from the heading. 
When the cable is extended to full length, perhaps i,ooo feet, 
the telephone should be advanced to a point as near the heading 
as possible and the extra cable reeled up once more. 

INCIDENTALS 

Among the many devices used to save time and promote 
efficiency underground, those of the simplest are the hose sup- 
porter and the drill rack, both of which can be made readily 
by any tunnel blacksmith. The former consists merely of two 
telescoping pieces of iron pipe, the length of each being about 
three-fourths of the width of the tunnel. In operation the hose 
is placed over the pipes, which are then extended until their 
pointed ends fit into convenient niches on either side of the 
tunnel near the roof; the pipes are clamped into position firmly 
by a threaded key which is provided for this purpose. By 
using two or three of these spreaders the hose are kept clear 
of the shoveler, who is thus saved no Uttle trouble and annoy- 
ance and is able to work to better advantage. The latter device 
is simply a rack for separating different lengths of drill steel. 
A satisfactory form consists of an A frame made of 4-inch by 
4-inch timbers, into which iron pegs are driven at convenient 
intervals. The segregation of the sharp drill steels on this rack 
enables the helper to pick out the proper length with assurance 
and dispatch. 



CHAPTER XI 

DRILLING METHODS 

The discussion of methods of tunnel construction in this and 
following chapters will be restricted chiefly to those employed 
where the entire cross-section is excavated in one operation. The 
majority of tunnels and adits driven for mining work, and many 
tunnels intended for irrigation and water supply, are small enough 
to be driven in this manner ; but in the construction of the larger 
undertakings, such as are required for railroad or similar purposes, 
it is customary to drive a pilot tunnel or heading, as it is some- 
times called — although the term is also employed to designate the 
advancing end of any tunnel — in front of the main body of the 
work which then consists in enlarging the smaller excavation to 
full size. The latter method, in addition to lowering the average 
cost of the entire work, since the process of enlarging is much 
easier and less expensive than that of driving the heading, also 
gives a valuable preliminary insight into the conditions which 
must be encountered later by the main tunnel, and enables the 
constructor to anticipate emergencies and make provision for 
them in his plans, thus aiding to prevent accidents and loss. 
Since, however, the scope of this bulletin is to be confined chiefly 
to mine adits and small tunnels, a discussion of the various phases 
of the ''heading and bench" system cannot be treated here as 
such, although the methods used in excavating in one operation 
the entire section of a small tunnel are in most cases appHcable 
to the driving of headings for larger tunnels. Local conditions 
at each project necessarily modify methods to such an extent that 
it is impossible to make a general analysis to fit all cases, but the 
discussion is intended to bring out some of the more important 
features of the methods employed in the various operations 

208 



DRILLING 209 

of drilling, blasting, mucking, and timbering, as they are applied 
to the driving of mine adits and tunnels. 

NUMBER OF SHIFTS 

One of the chief advantages claimed for the single drill 
shift per day method is economy. By having, the debris cleared 
from the heading by the shoveling crew at a separate time, the 
drill men upon reaching the face are enabled to start immediately 
to work setting up the machines and preparing to drill the ground; 
there is therefore no waste of time or labor on the part of these 
men or the helpers in shoveling out debris preparatory to mount- 
ing the drills. This method is especially economical when 
vertical columns are employed. During the process of drilHng 
the operators and their helpers are not interfered with or hin- 
dered in any way by the shovehng crew, and there is therefore a 
saving of that loss of motion which can hardly be prevented 
when two crews are working simultaneously in the heading. 
Moreover, since there is no delay in getting started, it is ordinarily 
possible to complete the round of holes within the allotted time, 
and even if this cannot be done plenty of extra time is available 
without delaying the following shift. The drilUng and mucking 
shifts can be distributed so that there is no loss of time and 
wages while the men are waiting for smoke and gases produced 
in blasting to be removed from the tunnel — a matter of cardinal 
importance where the provisions for ventilation are inadequate. 
These considerations all go to support the contention that the 
actual excavation cost per foot of tunnel is lower with this method 
than with other systems. 

On the other hand, by employing a single drill shift the daily 
progress in driving the tunnel is necessarily limited to the advance 
gained from the one attack, and therefore the completion of 
the work must inevitably be delayed. Most tunnels are prac- 
tically worthless until completed. If their construction is not 
pushed as rapidly as possible, not only is the capital invested in 
the equipment, tools, etc., securely tied up much longer than 
necessary and the cost for interest and the depreciation charges 
proportionally increased, but there is also a delay in the realiza- 



210 MODERN TUNNELING 

tion of the benefits to be derived from the tunnel, which in most 
cases is more than sufficient to offset any saving in excavation 
cost. For example, if an adit is being driven to drain a mine, 
the extraction of additional ore below water level is greatly 
delayed; or if the adit is intended to lower the cost of trans- 
porting the ore to the surface, the loss on the additional tonnage 
handled in the old way, owing to the delay in its completion, 
should be charged against this system of operation. Similarly 
with an irrigation tunnel, the entire season's crops may be lost 
from the longer time required to complete the tunnel if it is 
excavated by the one-shift method. Then again, the cost for 
administration and many other of the fixed charges are operative 
during the period of construction, independent of the number 
of shifts per day, and since the daily progress increases with 
the additional attacks per day, the proportionate charge against 
each foot of tunnel driven will be smallest when the greatest 
number of shifts are employed. Although, owing to a saving 
of the time and wages of workmen, there is an apparent economy 
in the cost of excavation by the one-shift method, when factors 
which reach deeper are considered, it will be found in most cases 
that the real and ultimate cost of the tunnel will be lowered by 
methods which make directly for speedier completion. 

Greater progress is undoubtedly attained with two shifts 
per day than with one, and if the work is properly organized 
there need be but little added excavation cost. It is the usual 
custom with this system to have the shovelers start work some- 
what in advance of the drillers, and to work first at removing 
the broken rock directly at the face to make it possible for the 
drillers to set up their m;achines promptly. At some adits aad 
tunnels where two drill shifts were used, the drilling and mucking 
took place simultaneously, the drillers themselves attending 
to the work of clearing out for the set-up. Of these two methods 
the former is preferable, not only because it economizes the 
time and exertion of higher-priced men, but also because the 
length of time when both crews are at work together in the 
heading — and consequently the inevitable amount of inter- 
ference and interruption — is thereby lessened. At a few places 



DRILLING 211 

three crews of shovelers were required to remove the rock 
broken by two drilling attacks. This system is obviously ex- 
pensive because the cost of the extra shovelers must be charged 
against a footage but slightly, if indeed at all, increased by their 
efforts, and it entails, for two of the three shifts, the disadvantage 
of simultaneous work just mentioned; it is therefore not desir- 
able. When it must be resorted to it. may usually be taken as an 
indication that a change which would permit its discontinuance 
should be made either in the length of the holes drilled and 
blasted or in some of the other methods of work. 

The consensus of usage at tunnels and adits where the best 
results in driving have been achieved, both in this country 
and abroad, leads to the conclusion, however, that the three- 
shift system of attack is the most desirable. This method has a 
number of opponents who charge against it four chief disad- 
vantages: (i) that time is lost on the part of the drill men in 
getting the machines set up and in operation; (2) that the 
greater number of men crowded in the restricted space of the 
heading are in one another's way, and therefore unable to work 
to the best advantage; (3) that the men must be paid for time 
wasted in waiting for the smoke and gases produced in blasting 
to be cleared from the heading; (4) that the system makes 
no provision for delays due to adverse conditions. As will 
be pointed out shortly, the time consumed in setting the 
machines up can be made negligible by the use of suitable 
methods of mounting and by properly directing and blasting 
the round of holes. A certain amount of crowding is, of 
course, unavoidable, but it is more than offset by the gain in 
efi&ciency from the various incentives which can result only 
from the three-shift method. To begin with, the shovelers have 
constantly before them the necessity of removing the waste rock 
before the drillers have finished their work, and are therefore 
unconsciously speeded up by the competition. At the same 
time the drill men endeavor to have their holes finished by the 
time the tunnel is cleared in order that no delay may be attributed 
directly to them. And both crews are inspired to better work by 
the knowledge that a competing shift is to follow immediately 



212 MODERN TUNNELING 

upon their heels, taking their places and performing similar 
work. Then, too, after the holes are drilled the extra men 
from the shoveling crew are of great assistance in taking down 
the machines and removing them, together with the mountings, 
hose, tools, and other articles that must be taken to a place of 
safety during blasting. As to the time wasted in clearing the 
tunnel of smoke, if it is properly and adequately equipped with 
ventilating apparatus this operation should require Httle more 
than fifteen minutes — just long enough for the men to eat their 
lunches, which time would have to be lost at any rate. Delays 
of course cannot always be prevented, but the men are encour- 
aged by rivalry to reduce these to the minimum, knowing that 
their work is to be compared with that of the shift to follow. 
These answers to the various objections are in no sense theories, 
but are deductions from actual observation and a study of con- 
ditions as they existed at tunnels and adits where some of the 
most efficient work in this country was being performed. 

The ideal results of the three-shift method, to be sure, are 
obtained only through perfected organization and good man- 
agement, but they utterly disprove the contention that efficient 
work is not possible under those conditions. That it is capable 
of the most rapid progress has never been gainsaid, and with 
proper handling the actual cost of excavation per tunnel-foot 
need be but little if at all greater than with other methods ; while, 
as has been shown, in most cases the system affording greater 
speed is within limits ultimately the more economical one. For 
these reasons, unless the conditions are indeed exceptional, the 
employment of three drilling shifts per day is recommended, 
and the discussion of other phases of tunnehng methods which 
follow will, unless otherwise noted, be predicated upon the 
assumption that three drilHng shifts are being employed. 

MOUNTING 

American tunnel practice is almost equally divided between 
the horizontal-bar and the vertical-column methods of drill 
mounting. The former consists essentially of an iron pipe, 
4 to 6 inches in diameter, a Httle shorter than the average width 



I 



DRILLING 213 

of the heading, and provided with a solid head at one end and a 
jackscrew with a capstan head at the other. The latter, which 
is rarely employed with more than two driUing attacks per day, 
is usually provided with a yoke and two jackscrews at one end, 
and its length is somewhat less than the height rather than the 
width of the heading. In several notable European tunnels a 
drill carriage was employed, however, so that a discussion of 
this method of drill mounting should not be omitted. 

The system employed with horizontal cross-bar method of 
mounting rock drills can perhaps be best illustrated by a descrip- 
tion of the procedure at the Laramie-Poudre tunnel. As soon 
after the blasting as ventilation permitted (ordinarily ten to 
fifteen minutes), the workmen returned to the face from a posi- 
tion of safety 1,500 to 2,000 feet away, bringing with them an 
ordinary tunnel car containing the cross-bar, drilling machines, 
tools, hose, etc. The three drillers, with the assistance 
of the foreman, first removed any loose rocks from the 
roof or walls which might fall later and possibly cause injury. 
This accomplished, they next cleared a space in the top of the 
rock pile, for two or three feet back from the face of the tunnel 
and perhaps four or five feet from the roof, in order that they 
might have room to work when drilling. Because of methods 
of blasting especially employed for this purpose, the rock pile 
usually occupied but a small part of this space, so that ordinarily 
but little work was required to clear it out. In the mean time, 
the helpers were expected to unload the bar and machines 
from the car, placing them on the rock pile conveniently at hand, 
and to connect the hose to the air and water mains. As soon 
as a proper space was cleared out, the bar was picked up by 
the drillers and helpers and held in position transversely across 
the tunnel at a measured distance from the face and roof, as 
directed by the foreman, where it was blocked, wedged, and 
finally screwed as tightly as possible in place. The drill men 
then placed the machines upon the bar and started drilHng as 
soon as the helpers completed connecting the hose to the drills. 
The necessary holes having been drilled from this position of 
the bar, and the waste rock having been removed in the mean 



214 MODERN TUNNELING 

time by the shovelers (an operation which was carried on simul- 
taneously with drilling and which ordinarily was accomplished 
before the drillers had finished), the machines were taken off, 
the bar was lowered and set up again about eighteen to twenty- 
four inches from the floor, the drills were replaced, and one or 
two holes were drilled by each machine from this position of the 
bar. The machines and the bar were then placed in a tunnel 
car and removed from the heading during the blasting. This 
method, sometimes slightly modified, was used at several other 
tunnels and adits with almost equally good results. 

The procedure with the vertical-column method of mounting 
is similar to this in some respects, but there are also some im- 
portant distinctions aside from that of upright position. Owing 
to the vibration produced by the drills, neither method of 
mounting will give satisfaction unless the bar is firmly jacked 
against solid rock. The amount of vibration is intensified 
and the need of a substantial foundation is much greater in the 
case of the vertical column, because the drills are usually mounted 
on cross-arms projecting from the columns at right angles, 
thus affording a leverage for any movement of the drill. It is 
therefore necessary to remove all of the waste rock from the 
space immediately in front of the face of the tunnel prior to 
drilHng in order that the foot of the column may rest upon the 
soKd floor, which, at the two or three tunnels where this method 
was employed with the three-shift system, caused considerable 
delay even under normal conditions. But in the majority of 
places where this method of mounting was employed not more 
than two drilKng attacks were attempted per day, and the extra 
work of clearing away was performed by the crew of shovelers 
before the drillers started work. 

The best results with the carriage mounting for drills were 
obtained during the construction of the Loetschberg tunnel 
through the Bernese Alps. In the first type of carriage em- 
ployed there, the horizontal bar carrying the drills was mounted 
at the end of a steel beam which was pivoted to a truck and 
counterbalanced at the other end by a heavy weight. Before 
this carriage could be brought sufficiently near to the face, 



I 



DRILLING 215 

even with the long beam, for the cross-bar to be jacked in posi- 
tion, it was necessary to clear quite a large passageway through 
the center of the rock pile down to the floor. In doing this, 
part of the material was carried away, and the remainder piled 
on either side of the tunnel to be carried away during driUing. 
When the passage was finished, however, the carriage, with the 
cross-bar and drills mounted upon it and extending longitudinally, 
was quickly rolled to the face, the bar swung around and 
jacked into position, and the drills were at once started to 
work. 

This carriage was superseded by one which abohshed the 
counterbalanced beam and carried the drill bar directly upon 
a short post mounted on the truck. With this device practically 
all of the broken rock had to be removed from the heading before 
the carriage was brought to the face, after which, however, the 
drills started promptly at work. 

One of the most important factors to be considered in choosing 
a method of mounting for tunnel work is the time required to get 
the drills in operation after blasting, including not only the 
actual time employed in setting up the necessary apparatus, but 
also the time consumed in the preparatory work of clearing 
away debris. The time spent in waiting for the smoke to clear 
is of course independent of the method of mounting, and can 
therefore be ignored in this connection. With the horizontal- 
bar system used at the Laramie-Poudre tunnel, the time normally 
employed in mucking back was rarely more than fifteen to twenty 
minutes. Jacking the bar in place occupied from five to ten 
minutes, and attaching the drills and making the water and air 
connections usually required from ten to fifteen minutes. The 
entire operation thus consumed under ordinary conditions from 
thirty to forty-five minutes, but it was not at all unusual, where 
circumstances were favorable, for the drills to be in operation 
within twenty or twenty-five minutes from the time the drill 
men reached the heading. At other tunnels and adits using 
this system the time required for similar work was reported as 
from thirty to sixty minutes. Owing to the much greater 
amount of material to be cleared out when the vertical-column 



216 MODERN TUNNELING 

method is employed, the time consumed in getting the drills in 
position to start work at adits and tunniels where the three- 
shift system was used ordinarily ranged from two and a half 
to four hours, and even under the most favorable circumstances 
was rarely less than two hours. The time spent in the Loetsch- 
berg tunnel in removing the waste rock was approximately one 
and a half hours with the first type of carriage used and from 
one and a half to three hours with the later model; but in order 
to accompHsh this, nearly twice as many men were employed at 
the work as are usually found in American tunnel headings. 
After the Loetschberg tunnel was cleared of the necessary 
amount of debris, however, the machines could ordinarily be 
started in from five to ten minutes. 

Aside from the question of the time consumed in clearing, 
the amount of waste to be removed has another bearing on the 
problem of choosing a mounting. In order that there may be 
no delay in getting the drills at work, usually the attempt is not 
made to remove the waste rock entirely from the heading before 
the mountings are set up, much of it being merely shoveled to 
one side and removed later. This prehminary work is often 
performed by the drill men, especially with the three-shift 
system ; and where (as in the case of the vertical-column method) 
there is a great deal of it to be done, by the time the men have 
the machines set up and are ready to start drilling they are pretty 
well tired out and consequently cannot work so rapidly and 
efficiently in drilHng the required holes. Even if the work is 
performed by the regular shoveKng crew, these men certainly 
are not stimulated by the knowledge that they are performing 
dead work and that every shovelful handled in clearing back 
must be moved again later. This disadvantage obtains not only 
in the three-shift system, but in many cases in which two shifts 
are employed, and the shoveling crew start ahead of the drill 
men and commence work clearing away the face for a vertical 
column set-up. The horizontal-bar and, to a lesser degree, the 
drill-carriage methods have the advantage of requiring a much 
smaller proportion of duplicated work. 

The adaptabihty of the mounting for the work required of 



DRILLING 217 

it after the drills are in operation is another factor to be reckoned 
with. The advocates of the vertical-column method claim 
that it enables the holes to be placed to better advantage, and 
this is quite truly the case where piston drills are employed. 
But hammer drills mounted on a horizontal bar can place the 
holes just as effectively, if not more so. But with either type 
of machine the drill carriage is badly handicapped. It was 
discovered with those used in the Loetschberg tunnel — and the 
same disadvantage was experienced at an adit in this country 
where a similar drill carriage was tried and soon abandoned — 
that it was impossible to point the inclined holes in such a way 
as to secure the maximum efficiency from the explosive used. 
Therefore, in order to make the holes break to the bottom it 
was necessary to use heavier charges of explosive, and the holes 
were not drilled as deeply as they might otherwise have been. 
The shallower holes made it necessary to spend a greater per- 
centage of the day's labor in the unproductive preparatory work 
of setting up and tearing down the drills, and increased the 
opportunities for delays in blasting. Then, too, it is impossible 
with one set-up of a horizontal bar, such as was used in the 
carriage method of mounting, to make the holes near the bottom 
of the tunnel sufficiently horizontal to secure an even floor, 
necessitating trimming and causing trouble in maintaining the 
proper tunnel grade. 

The fact must not be overlooked, however, that with the 
carriage method drills are subject to less wear and tear because 
they are kept on the bar continually and are not thrown around 
on the floor and muck-pile. When this is permitted the drills 
are apt to become filled with sand, grit, etc., and because of 
friction and abrasion, the cost of repairs is increased. Nor 
should the facihty in changing to a new hole possessed by the 
horizontal bar and the drill carriage be disregarded. When 
these methods of mounting are employed, all that is necessary 
in starting a new hole is to slide the drill along the bar and 
clamp it in place, but with the vertical column not only the 
machine, but the cross-bar as well, requires adjusting; since the 
adjustment is a vertical instead of a horizontal one, the entire 



218 MODERN TUNNELING 

weight of both drill and cross-arm must be lifted or sustained 
at nearly every change. 

Taking, then, all of these factors into consideration, the 
horizontal bar proves to be the method of mounting drills best 
adapted for tunnel work. Its use enables the drills to be put in 
operation with the least loss of time and by the smallest number 
of men. It requires the rehandHng of the minimum amount 
of waste rock, §o that the drill men are not fatigued before they 
start drilling or the shovelers disheartened by dead work. It 
permits directing the holes in such a way that the maximum 
strength of the explosive is utilized, drilling deeply so that 
too great a portion of the time need not be spent in preparatory 
work, and placing the holes to insure the breaking of the roof 
and floor smoothly and at the desired grade. It is especially 
adapted for use with the more rapid-driUing hammer machines 
and lends itself readily to removal when necessary. In common 
with the vertical type it is subject to the danger of allowing 
grit to become lodged in the machines, but this can be partially 
prevented by care in handling. These considerations render 
the use of the horizontal bar highly desirable where an efficient 
method of mounting drills for tunnel work is desired. 

NUMBER OF HOLES 

Any determination of the proper number of holes to be used 
in driving a tunnel or adit of a given size is dependent upon 
several factors. A large number of holes in which a greater 
charge of explosive may be placed expedite the operations of 
driving, because the heavier blast tends to hurl the rock farther 
away from the face, and thus not only saves time in setting 
up the machines, but also gives the shovelers more room and 
enables them to work to better advantage on more widely 
scattered material. But, at the same time, holes that are not 
strictly a necessity entail an extra expense not only for the 
explosive used in them, but also for the time required in drilhng. 
This is especially true in those cases in which the drilling work 
requires more time than the operation of removing the rock, 
and hence any extra holes would delay both crews. If the proper 



DRILLING 



219 



O\00 lO 
•-I CO O 

lo o t^ 



T*-lO 






lO '+ 



rO 






<U o 





On 


O 


<-< 


»oo o : ; ; 


: : ! : ^ 


to : : 


'. '. f^ '. 


lo loio ; ; ; 


! ! ! ! n 


o : : 


'. '.'^ '. 




vO 


T}- 


CI 



c o c ij 

2 2i rt cr 



lOO o ion t^iOiO 






c^^. 


dj 


C biO 


c 


o 


o 


?J 


1, 


gc 


.S,f2 


JO 


Jc/^ 



J" .2 .2 



mOO< 



o 
u 

G 
c« 

i oJ 
en *^ 
O rt 



bfi- 



5 cj 0) rt 
2 .ti .ti -o 12 



^ rt Gj 



03 TJ 



(V 



^ .^ ,^ ,^'^ aj.2 o 



- 2^ J- ^ - - 






S «:J rt rt 2 2 c^ 



o 9 






??? 


lO 


OS i-H lO 

HH (N « 





•^ i c? I ' 



03 



"3 03 <l^ 
Tic ti 
3 3 03 

CQCQU 



3 

-o 

3 

cr-M 

<g 

=3-0 

1^ 



s 



u : O.O 



3== 
21 



OJ3 O O >- ^-3 03 03 o'^'-"-' ^^-^^i:^ 



220 



MODERN TUNNELING 



<v u 
c o 



s p 



£ 2i C3 C 



o 


0» 




lO 




"sl-n 


I^ 


M 


t^ o 


\o 


o 


in 


CO 


ro Tf 



00 CO 



I I 

GO O 









ct3 

C c C a; 
o c o.ti 



(U ^ 2 



(N 7 7 ^0) <s, ^ 

(M I l-l I— I 1-r 



C^ Ol 



O) 



00 \0 






— <3Jr3 Ojii <L)— (U>> 

a 03 cti o 2 c a'Z! i; -2 OS 



DRILLING 221 

number of holes is being used, the major portion of the rock 
should be broken into fragments small enough to be shoveled 
readily, although an occasional boulder, because of the relaxa- 
tion it affords the workman from the steady grind of shovehng, 
is said to expedite rather than retard the speed with which the 
spoil can be loaded into the tunnel cars. 

The central factor and starting point, however, in a just 
determination of this question is undoubtedly the physical 
character of the rock being penetrated, which is never twice 
aUke in different locahties, and it is generally necessary to experi- 
ment at first in order to discover what number of holes will 
indeed produce the best results. Generally speaking, igneous 
rocks require more holes than sedimentary rocks, but there are 
wide divergences in both classes. The holes must be more 
closely spaced for a tough rock that is close-grained and massive 
than for one that is brittle and easily shattered, even though it 
may be harder and more difficult to drill. Bedding or joint 
planes or joint cracks are of great assistance, and a rock in which 
they occur will be more easily broken and hence require fewer 
holes. The preceding table shows the number of drill holes used 
in American tunnels penetrating different classes of rock. 

DIRECTION OF HOLES 

Chiefly because of the great influence of local conditions, the 
arrangement of drill holes is rarely identical at any two tunneling 
projects. For reasons to be explained later, however, it is cus- 
tomary to drill a part of the holes (called the ''cut" or "cut 
holes") in such a manner that when blasted they will first remove 
a core of rock from the solid face of the heading, thus decreasing 
the work to be done by the remaining holes. Practically all of 
the various means of arranging drill holes in the headings of 
American tunnels may be summarized as follows into three main 
types, according to the kind of cut employed. 

The wedge or ''V" cut is the one most commonly employed 
in tunneling operations in this country. It consists essentially 
of several pairs of holes directed toward each other from opposite 
sides of the heading in such a manner that when properly charged 



222 MODERN TUNNELING 

and exploded they will break out a wedge-shaped core of rock 
usually extending from the roof to the floor of the tunnel. Figure 
58 shows a typical wedge-cut round similar to the one employed 
in driving the Buffalo Water tunnel. Holes numbered i to 8 
comprise the cut and were blasted simultaneously by electricity, 
while 9 to 14 are the side holes, and were next fired together, 
and 15 to 18 are the back or dry holes and were exploded last. 
Such a round must necessarily be changed somewhat where the 
heading is arched or semicircular. Figure 59 illustrates such 
a round, similar to those used in driving the heading of the 
large siphons on the Catskill Aqueduct. In this case holes i 
to 6, comprising the cut, were blasted together, followed by 
holes 7 to 12, which were called relievers, and finally by 13 to 
22, which were called trimming holes. 

Either vertical columns, as was the case in the two examples 
just cited, or a horizontal bar may be used to mount the machines 
when drilling this type of round, but where the majority of the 
holes are to be drilled from one position of a horizontal bar the 
location of the holes must , necessarily be somewhat modified, 
although the general arrangement still remains a wedge-cut 
round. Figure 60 shows such an arrangement, similar to the 
one em-ployed at the Laramie-Poudre tunnel. Holes Nos. i and 
2 were called short-cut holes, Nos. 3 to 6 long cuts, Nos. 7, 
8, 9, 10, 19, and 20 relievers, 11 to 14 sides, 15 to 18 backs, and 
Nos. 21 to 23 lifters, the numbering indicating the order of 
blasting. The lifters, and two relievers (Nos. 19 and 20) which 
were used only in hard ground, were the only holes drilled from 
the lower position of the bar. Three machines were employed in 
drilling this round, and the following table (page 224) shows 
the holes drilled by each and the order of drilling (lettering 
the machines A, B, and C from left to right when facing 
the heading). 

A somewhat similar round was used with a horizontal bar 
at the Rawley tunnel, and there are, of course, many other 
variations of the V-cut arrangement of holes, but these figures 
illustrate the principles underlying the more common ones 
employed in tunnels and adits in this country. 



I 




Fig. 58. Wedge-cut round of holes. 




Fig. 59. Modified wedge-cut round for arched heading. 




Fig. 60. Wedge-cut round drilled from a horizontal bar. 



224 



MODERN TUNNELING 



ORDER OF DRILLING FOR EACH MACHINE AT LARAMIE-POUDRE 

TUNNEL 



Machine A 


Drill-hole 
numbered 


Machine B 


Drill-hole 
numbered 


Machine C 


Drill-hole 
numbered 


i ' 

O 2 

1 3 

a 5 

a 7 


17 
II 

5 

13 

7 

I 

19 


I 
2 

3 
4 

5 


l6 
10 

15 
9 
3 


I 

2 

3 
4 
5 
6 

7 


i8 

12 

6 

14 

8 

2 
20 


Lower 
position 

00 


22 


6 


21 


8 


23 



The second general, type of cut frequently employed will be 
designated as the pyramid cut, consisting usually of four cut 
holes drilled in such a manner that they meet, or nearly meet, 
at or near a common point — generally near the axis of the tunnel 
— and when properly blasted they remove a more or less pyra- 
midal core. Figure 6i shows a round of this type similar to the 
one employed at the Yak tunnel, in which the cut holes numbered 

I were blasted simultaneously, 
followed by the remaining holes 
in the order indicated. In most 
of the instances observed by the 
authors, the pyramid cut has 
been employed with vertical col' 
umns, but it can be drilled just 
as efficiently with the horizontal 
bar by drilHng two or possibly 
three holes with each machine 
from the lower set up. Figure 62 
shows such a round. 

The third type is the bottom 

or draw cut which was employed 

at several places visited, the one at the Carter tunnel illustrated 

in Figure 63 being typical. The holes were blasted in the order 

indicated, Nos. i to 3 comprising the cut. 




Fig. 6] 



Pyramid-cut round 
of holes. 




Fig. 62. Pyramid-cut round for use with 
horizontal bar mounting. 




226 MODERN TUNNELING 

It can easily be proved theoretically that where a bore hole 
is drilled in a homogeneous mass of rock the maximum efficiency 
can be obtained from a suitable charge of explosive placed in it 
when the line of least resistance (by which is meant the shortest 
distance from the charge to a free surface of the rock) is at 
right angles to the axis of the bore hole, and that the minimum 
efficiency will be obtained when the two are coincident. And 
practically, although a homogeneous rock is a rarity and hence 
the actual results will be influenced quantitatively somewhat 
by the various features of rock texture such as joints, cracks, 
fault fissures, bedding planes, etc., the results have been found to 
agree in the main with the theoretical deductions. It is obvious, 
therefore, that in the heading of a tunnel or adit where but one 
free face can be obtained, it is impossible to drill and blast a 
single hole in such a manner that the maximum efficiency can 
be obtained from it. But by drilling a number of holes arranged 
according to any of the preceding systems, and blasting the 
cut first so as to create more free surface, much better results 
can be obtained from the holes which remain. It is for this reason 
that the position and direction of the holes comprising the 
cut are generally considered the most important feature of the 
work, the spacing of the remaining holes being admittedly 
merely a question of having them sufficiently close together to 
break the rock into fragments of the required size for facile 
handling. 

When the wedge or V-cut is employed, the several pairs of 
holes should be placed close enough together for them to be of 
some mutual assistance. This is especially true when the entire 
cut is exploded simultaneously. What this distance shall be 
is controlled almost entirely (as in the determination of the 
proper number of holes) by the character of the rock, its tex- 
ture, toughness, the presence of cracks and bedding planes, etc. 
Its determination is often made by the foreman in charge, and 
if he is a man of wide experience, satisfactory results may follow; 
but the general efficiency of the work will often be increased 
greatly if experiments are made at the outset to determine just 
what combination will give the best results for the particular 



I 



DRILLING 227 

rock being encountered. It follows, of course, that such experi- 
ments should be repeated whenever a marked change in the 
nature of the rock is observed. 

In order that the line of least resistance may approximate as 
closely as possible the perpendicular to the axis of the drill hole, 
the angle between opposite holes in the cut should be as large 
as can be obtained with any given depth of round. From this 
it follows that the drill holes should start as near as possible to 
the opposite sides of the heading; but obviously the full width 
of the heading cannot be utilized because provision must be 
made for the feed screw and crank of the drill, which usually 
extend three to four feet from the face. This works especially 
to the disadvantage of narrow headings, because in them a 
greater proportion of the actual width must be sacrificed for 
this purpose. But with broad headings the marked advantage 
of a wide angle is easily secured and possibly offers an explana- 
tion of the popularity of the wedge-cut system in such cases. 

Of even greater importance than the necessity of securing 
a wide angle between opposite holes is that of drilling them so 
that they meet, or at least bottom near enough to one another 
to be detonated simultaneously by the one first to explode. 
Owing to mechanical reasons, the width of the drill bit, and hence 
the size of the hole, must be decreased with each successive 
change of steel, and as a result the hole is necessarily smallest at 
its bottom end — the place where the explosive is most needed 
and where it is extremely desirable that the hole should be a*s 
large as possible. Omitting from consideration the expedient 
of chambering (that is, the enlargement of the bottom of the 
hole by the explosion of a small primary charge before loading 
it with the main portion of the explosive) which consumes en- 
tirely too much time to be considered for rapid tunnel driving, 
the defect can be overcome to a surprisingly large degree by the 
simple resort of connecting the drill holes, which concentrates 
the explosive at the point of the ''V." When fuse firing is 
employed, it is extremely essential that the holes be so directed 
that they are intercommunicating (or so nearly so that both 
holes will detonate together) or the desired effect will not be 



228 MODERN TUNNELING 

gained, but when electric firing is employed direct connection, 
although very desirable, is not so absolutely essential. 

But in addition to the mere concentration of explosive thus 
secured, the combined efficiency of the two charges is much 
greater than when they are exploded separately. Assuming, 
again, that the holes are drilled in homogeneous rock and that 
they make equal angles with the shortest hne from their junction 
to the free face, if both are loaded with identical charges of 
explosive and detonated simultaneously, their maximum break- 
ing effect will be exerted along the resultant of their combined 
forces, which in this theoretical case coincides with the shortest 
distance to the free face (the line of least resistance). Practi- 
cally, of course, this will be somewhat modified; but it is a 
well-established fact that where the ground is tough and difficult 
to break, much better results are obtained when the cut holes 
are directed and drilled to intersect; although, unfortunately, 
this is not widely known, as evidenced by the too great number 
of cases observed in which no attempt was made to connect the 
cut holes. 

Practically the same conditions prevail with the pyramid 
cut. The number of holes comprising it may vary from three 
to six or even eight, according to the nature of the ground; 
and the proper number can best be determined by experiment. 
It is just as necessary to drill the holes with the widest possible 
angle between them, and it is even more essential that they meet 
in a common point, because one of the main advantages of this 
cut is the concentration of a greater amount of explosive at the 
narrow apex of the core of rock to be removed. All these advan- 
tages are thrown away if the charges of explosive in the different 
cut holes are not detonated simultaneously. 

The bottom cut, as it is usually drilled in practice, although 
it often enables the attainment of a wider angle between the axis 
of the drill hole and the line of least resistance, disregards entirely 
the important advantage to be obtained from connecting drill 
holes, and this circumstance, in the opinion of the authors, should 
be sufficient to prevent its use under any but exceptional condi- 
tions. For mine adits, however, whose excavation must of neces- 



I 



DRILLING 229 

sity provide sufficient head room but whose lateral extent is 
limited, in which it would be impracticable, if indeed possible, 
because of the narrowness of the heading, to drill an effective 
wedge, or a pyramid-cut round, the bottom cut furnishes the 
only solution of the difficulty. In this event it is recommended 
that the cut holes be drilled from as near the top of the heading 
as possible, and directed in such a manner that they will connect 
with holes that are usually considered Kfters, and that both 
be detonated together. 

DEPTH OF HOLES 

During the past four or five years there has been some differ- 
ence of opinion among students of the problems of tunnel driving 
as to the proper depth for drill holes in tunnel headings. In 
view of some of the remarkable results attained in driving the 
Simplon and Loetschberg tunnels, where, as is admitted by 
every one, the holes were much shallower than those in American 
practice, the question has been raised whether the holes in tunnels 
of this country are not drilled too deep. Numerous tables have 
been prepared in support of this argument, in which it appears 
that at most of the European tunnels the progress is much 
greater (in some cases more than double) than that of tunnels 
in America. But at the same time, consideration is not always 
given the fact that in many instances these records are in their 
nature in no wise comparable; for in Europe, at the majority 
of tunnels thus cited, the work was conducted throughout the 
entire twenty-four hours of each day, while in America in many 
instances but two (and indeed in some only one) shifts were 
employed daily. Then again, the nature of the rock exerts an 
all-important influence upon progress, and in many cases this 
has been to the advantage of the European tunnels. A notable 
example of the influence of the rock encountered is found at the 
Loetschberg tunnel, where the same methods and practically the 
same equipment were employed at the different ends, the one at 
north end working in limestone, and the other in the south end 
in gneiss and schist. The progress attained at the south end 
was much less than that of the north, and in some months the 



230 MODERN TUNNELING 

progress in the north end was nearly double that of the south. 
Other considerations also, especially the amount of labor and 
the cost of driving, enter into the problem in such a manner 
as to make it impossible to say (when everything is taken into 
account) that the greater speed in European tunnels is due solely 
to the use of extremely shallow holes. That in many instances 
the holes in American tunnel headings are too deep, however, 
is equally impossible of denial, and for these reasons a discussion 
of the factors which enter into the determination of the proper 
depth of holes is extremely desirable. 

One of the chief advantages arising from the use of shallow 
rounds is (when the holes are properly directed) the increased 
efficiency obtainable from a given charge of explosive; for, since 
the width of the heading is for all practical purposes constant, the 
angle between the line of least resistance and the axis of the 
bore-hole becomes a function of the depth of round, the width 
of the angle increasing with shallow holes. This advantage 
obtains especially with the wedge cut and with the pyramid cut, 
and it should be a fundamental consideration with the bottom- 
cut method of drilling the holes. Strangely enough, however, 
in the Loetschberg and the Simplon tunnels, which are so often 
cited as examples of the ''highly desirable" European practice 
of using shallow holes, this advantage was almost, if not entirely, 
thrown away, because the holes were drilled in vertical rows 
and were nearly parallel to the bore of the tunnel. In such a 
case the line of least resistance and the axis of the bore-hole are 
nearly coincident — a condition which results in the production 
of the least possible efficiency from the charge of explosive ; and 
it cannot be gainsaid even by the advocates of this method that 
a much greater quantity of explosive than is usual in American 
practice was required to break the same amount of rock. If 
to this is added the fact that such a system utterly ignores the 
advantage to be obtained from connected drill holes by the con- 
centration of explosive at the apex of the core of rock to be 
removed, there is strong ground for rational suspicion that the 
extreme shallowness of the holes used in these tunnels was adopted 
from necessity rather than from desirability; because with this 



DRILLING 231 

system of drilling and directing the holes the difficulty of blasting out 
the rock with deeper rounds could not fail to be greatly increased. 

Among other advantages of the use of reasonably shallow 
holes may be mentioned the fact that such a method allows that 
the holes be of larger diameter at their further end, increasing 
their capacity for explosive and enabhng its concentration at the 
point where it is most needed. This is one of the chief factors 
which makes even possible the European practice of employing 
extremely shallow holes, but it can hardly be denied that in this 
case much more effective results in blasting might be accom- 
plished by a change in the direction of the cut-holes. Besides, 
since, in America at least, the holes are rarely charged with 
explosive to their full extent, the mass of rock between the ends 
of the charges of explosive in the dift'erent holes and the free 
face of the heading (which can be considered as a measure of the 
amount of resistance to be overcome) is not so great with the 
shallow holes. This fact, or the customary use of relatively 
heavier charges in shallow holes, may explain, perhaps, why in 
such cases the major portion of the rock is usually thrown 
farther down the tunnel instead of being piled high immediately 
in front of the new face, with the double advantage of making 
it easier to load the rock and saving time in getting the drills 
mounted. It is fairly well established, also, that the rock tends 
to break into smaller fragments where shallow holes are em- 
ployed. And again, where deep holes are not employed the same 
care in starting them exactly at a given point is not required, 
nor is it necessary to direct them with such great accuracy — 
although, of course, the need of connecting the cut holes must 
not be overlooked. 

The principal and very serious disadvantage in using the 
shallow-hole round, on the other hand, and one that it is impos- 
sible to avoid, is the fact that in order to secure the same daily 
advance a proportionately greater number of drilHng attacks 
must be made. This results in a waste of time in driUing; for 
it is possible under ordinary circumstances to drill one hole of a 
given depth more rapidly than two holes of the same aggregate 
footage because of the time lost in changing to a new position, 



232 MODERN TUNNELING 

Starting, etc. But even granting that the difference in drilling 
time (perhaps because it is too small, or because in either 
case the drilling can be completed before the heading can be 
cleared of debris) is not an appreciable factor, each extra drilling 
attack required to secure the same progress causes a correspond- 
ing loss of time in loading and blasting the holes, in waiting for 
the smoke and gases to be removed, in clearing the debris from 
immediately in front of the face, and in setting up the drills, all 
of which is ordinarily dead work and cannot be avoided. This 
was seriously felt at the Loetschberg tunnel, because in the 
endeavor to compensate for it, it was necessary to employ four 
drills in the heading (6 feet x lo feet) ; and as a result the holes 
had to be drilled nearly straight, with disadvantages already 
described, because otherwise the drills in the center interfered 
seriously with the operation of those at the side. 

On the other hand, where the holes are too deep, as is some- 
times the case in America, the angle between the cut-holes may 
be so narrow and the mass of rock in front of the charge of 
explosive may be so great that it will be impossible for the cuts 
to break bottom on the first blast and thus the entire round is 
spoiled. The usual remedy in such cases is to blast the cuts 
separately and not to fire the remainder of the round until it 
has been ascertained by inspection that the proper depth has 
been reached by the cut-holes. A certain amount of delay can- 
not be avoided when this method is employed, even if the holes 
break to the end, for it is never possible to return to the breast 
for such inspection immediately after the cuts have been deton- 
ated. But when the cut-holes fail to break, the delay is greatly 
increased because the remaining portions must be cleaned out, 
reloaded, and fired, with an additional delay in waiting for the 
smoke to clear. 

This system was used at one of the Colorado tunnels, which 
at the time of first examination was being driven through some 
very tough rock, employing a round of holes slightly deeper 
than the average width of the heading. Holes of this depth had 
given satisfactory results in the somewhat more frangible ground 
previously penetrated, the round being drilled and blasted in an 



DRILLING 233 

eight-hour shift without difficulty; but upon striking the harder 
rock it became necessary to blast the cuts separately, and more 
often than not to reload and shoot them for the second and 
occasionally for the third time, the cycle being lengthened to 
about ten hours, while several times at least fourteen hours 
were needed. If three drilling shifts had been employed at the 
time, such a condition would have been fatal; but since but two 
attacks were being made the diflerence was not so noticeable, 
though even in this case the cost of the extra explosives required 
and the overtime wages of the men added a considerable amount 
to the expense of the tunnel work. Shortly after the first 
examination of this tunnel by the authors, however, the depth of 
the rounds was reduced to about 75 per cent, of the width 
of the heading. This made it unnecessary to load and shoot 
the cuts separately, and instead of getting two seven-and-one-half- 
foot rounds in from twenty to twenty- two hours, by working 
three eight-hour shifts it was possible to drill and blast four, and 
sometimes five, live-foot rounds per day, thus increasing the daily 
tunnel progress from fifteen to nearly twenty-three feet with but 
a very small extra cost for labor. The consumption of explosive 
which was a very considerable item with the old system was also 
decreased fully 25 per cent., and the total cost of the tunnel per 
foot was greatly reduced. 

The disadvantage of too deep holes was strikingly brought 
out in the construction of the Laramie-Poudre tunnel. During 
the first part of the work a ten-foot round was drilled in a head- 
ing 9>^ feet wide, but the round was later changed to one of 7 
feet in depth with much better results. To be more specific, 
during the seven months from April i, 1910, to October 31, 1910, 
at the east end of the tunnel, 3,171 feet were driven, an average 
of 453 feet per month, using a ten-foot round; but during the 
next 84/5 months, from November i, 1910, to July 24, 191 1, 
when the tunnel holed through, 4,798 feet were driven, or an 
average of 545 feet, with a seven-foot round. This is an increase 
of over 20 per cent., in spite of the fact that the higher speed 
was made when the work was at a greater distance from the 
portal; and, since there was no essential change in method, 



234 MODERN TUNNELING 

equipment, or in the character of the rock penetrated, it is attrib- 
utable solely to the use of shallower holes. When the ten-foot 
holes were employed to secure an advancement of S}4 to 9 feet, 
it was unusual to be able to drill and blast more than two rounds 
in twenty-four hours, and oftentimes not so many, as the aver- 
age of 14^ feet daily testifies; but with the seven-foot round 
not only could three attacks be made, advancing on an average 
6}4 feet per attack, but a comfortable margin of time was left 
to provide for delays and under favorable conditions this extra 
time meant extra footage. Thus in March, 191 1, the American 
hard-rock record of 653 feet, or over twenty-one feet per day, 
was established. This advantage of being able to complete an 
entire cycle of operations during a single shift should be given 
the weight in the problem it deserves. If crews of men could be 
found who would work as well without rivalry and without special 
incentive to push the work, it might be perfectly feasible to 
choose a depth of round that would require ten, or even twelve, 
hours to put it in; but under the present working conditions, 
where it is necessary to have some accurate measure of the work 
performed by each crew, a round is required for which the entire 
cycle can be completed during a single shift, with a sufhcient 
margin of safety to provide for any ordinary delay. 

It is, of course, impossible to set any definite standard or 
guide for the proper depth of hole which will be applicable to 
all cases. There are too many variables influencing the result. 
The proper depth can only be and must be determined by experi- 
ment in each individual case. But from an extended examination 
of American practice, investigating carefully the results obtained 
from the methods employed, from a careful analysis of European 
practice as far as could be found in published accounts, and 
from a study of all the available modern authorities, the authors 
are of the opinion that for the majority of cases the proper 
depth of drill-hole, the one which most equitably balances the 
advantages and disadvantages inseparable from the problem 
will be found after careful experiment to be a depth from 60 to 
80 per cent, of the width of the tunnel heading. The following 
table gives an analysis of American practice in this respect: 



DRILLING 



235 









<v 



c 0) 

JO 






o" 










03 


c 








03 


tuO 


o 

C 




en 

'33 
c 


^ 

rt 




Si 


OOcQO< 



<L) 



0) 









0) 
03 C 

)-, fl, QJ O 

•ii Xn ■ — oi c« 



CQO< UUKOc/)c^O0:ic)iO<OXOQj 



^T3 

*^ 5 

is- 

'— en 



oT 



.ti o.ti s 



aj 



(L) 01t3 ?J3 



r^oo o t^ oi o »o rfoo o 



(U S3: 






t>.oo 00 o 00 vc r^ lo iDvo o t^ t^oo OM^ r^ lo^o ovvo oo o o lovo o vo vo o -^ 



>-0 OJ3 



1^00 00 O 00 \0 t^ lO lO^ Gn l>> t>.00 ON t~» t>" lO^ ONVO 00 OvO lOiOO^vOO •^ 



Sf^ 



vr 3 o 



^ X X X X 5 

OOO OMOoOOOOOt^OOOOOONOOOOOvOQOOl^ONOlt^ lOO 04 vO t^vO »o ^ 



lO lO rf Tj- Th -rt- lO lOO O O) ON O) 00 00 lO »O00 On rO On r^ ON O O OnnO t^OO O t>. 



00 r^ 00 00 00 00 t^vo 00 ^ i-i \o 00 00 on t>. r^X) « o on r^ on no r^vo o r^vo oo t^ 



a; e 
bjO O 

:> o 



ppoJOJiDCajpcjpS'c 



13 T3 TD 
bjObiObjObX)bjOO O bi0b.obflb)0tyo5 O 5 5 © biObiOtuObiObjOO biObJObobiOO _, 



3 



?5 c 



3 
O 



2 rt 



o 






3 03 OS 



§^^S^?t2P^S3 



OJ 05 2 J^, i- 



J= P-f. 



^.2 >:^ o > 

- __ QJ r; <V) 






<" o 9 ^ o «« o! 3, 



O a, 03 03 o. 



>^ OS 

>-. -t-J 

Ij Jj "•-' ^ 



CHAPTER XII 
BLASTING 

AMMUNITION 

To be suitable for use in tunnel work, as distinguished from 
surface blasting operations, an explosive should not produce any 
great amount of poisonous gases and should not easily, if at 
all, be affected by moisture. In common with other usages, a sub- 
stance is required here that is stable in composition and not 
rapidly deteriorated by frequent changes of temperature or other 
causes; it must not, as, for example, is the case with liquid 
nitroglycerine, be so sensitive to shock that safe transportation 
and handling are wellnigh impossible. Although under some 
circumstances, especially in tunnels that are not wet, an explo- 
sive called ammonia dynamite can be and is employed on rare 
occasions, the one which best fulfills the necessary requirements 
and the one which is almost universally used in tunnel work is 
known as gelatine dynamite. 

Gelatine dynamite is a combination of a certain amount of 
blasting gelatine (varying according to the strength desired) and 
a suitable absorbent. The former is made by adding a small 
percentage of gun-cotton (nitrocellulose) to liquid nitroglycerin, 
thus producing a jelly-like mass that has greater explosive qual- 
ities than either of its constituents, but which is much less sen- 
sitive to shock than nitroglycerine. The absorbent is usually 
some combustible material (wood pulp is frequently employed) 
to which has been added a sufficient amount of sodium nitrate to 
supply the necessary oxygen for its combustion. By the use of 
such a combustible absorbent, instead of the inert one formerly 
employed with straight nitroglycerine dynamite, the gases gener- 
ated by the burning of the wood pulp add to the volume pro- 
duced by the detonation of the explosive constituent, and the 
extra heat generated in this combustion adds greatly to the 

236 



BLASTING 



237 



total intensity of the reaction. Ammonia dynamites, which 
are a somewhat more recent discovery, consist of a combina- 
tion of ammonium nitrate and nitroglycerine absorbed in a so- 
called ^'dope" similar to that just described. The following 
tables * show typical compositions of commercial samples of these 
two kinds of dynamite : 

GELATINE DYNAMITE 



Strength 



Ingredient 





30% 


35% 


40% 


50% 


55% 


60% 


70% 


Nitroglycerine. . . 


23.0 


28.0 


330 


42.0 


46.0 


50.0 


60.0 


Nitro-cellulose . . 


0.7 


0.9 


1.0 


1-5 


1-7 


19 


2.4 


Sodium nitrate . . 
Combustible 


62.3 


58.1 


52.0 


45-5 


42.3 


38.1 


29.6 


materialsf .... 
Calcium 


13 


12.0 


130 


10. 


9.0 


9.0 


7.0 


carbonate. . . . 


I.O 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 



t Wood pulp used with 60 and 70 per cent, strength; sulphur, flour, wood 
pulp, and sometimes resin used in other grades. 

AMMONIA DYNAMITE 



Ingredient 



Strength 



30% 



40% 



50% 



6o< 



15 


20 


22 


27 


15 


15 


20 


25 


51 


48 


42 


36 


18 


16 


15 




I 


I 


I 


^ 



Nitroglycerine , 

Ammonium nitrate 

Sodium nitrate 

Combustible materialsj 

Calcium carbonate or zinc oxide . 



35 
30 
24 
10 

I 



t Wood pulp, flour, and sulphur. 

For further discussion of the nature and composition of 
explosives, which is hardly within the province of this book, the 
reader is referred to various pubHcations of the Bureau of Mines; 
they may be had upon appHcation to the Director, Bureau of 
Mines, Washington, D. C. 

The harmful gases usually resulting from dynamite are 
carbon dioxide and carbon monoxide. Although the former will 

* From a paper by C. T. Hall before American Institute Chemical Engi- 
neers, Washington, D. C. Meeting December 20, 191 1. 



238 



MODERN TUNNELING 



not support respiration, and when present in sufficient amount 
may cause unconsciousness and even death from strangulation, 
it has no very injurious effects when sufficiently diluted. The 
latter, however, is not only exceedingly dangerous, but its 
effects are also cumulative; indeed if air containing even a very 
small amount of it is breathed for any length of time, serious 
and often fatal results will follow. The fact that gelatine 
dynamite (with the possible exception of ammonia dynamite, 
which approaches it very closely in this respect) produces under 
proper conditions the least amount of carbon monoxide is one 
of its chief advantages for use in tunnel work. Even with this 
explosive, however, if the cap is not strong enough to cause a 
complete detonation, and even more especially when the dynamite 
burns rather than explodes, much greater amounts of carbon 
monoxide are formed; in addition there are many other harmful 
gases produced, among which may be mentioned the dangerous 
peroxide of nitrogen and hydrogen sulphide, the former of which 
is especially virulent. 

The following table shows the results of tests conducted by 
the Bureau of Mines concerning the kind and amounts of gases 
produced by the detonation of samples of various kinds of 
commercial dynamites. In making the tests a charge of 200 
grams (approximately 7 ounces) in the original wrapper was 
exploded in a Bichel pressure-bomb and the gaseous products 
retained and analyzed: 

GASEOUS PRODUCTS FROM EXPLOSIVES 



Elind of explosive 


§3 


6^ 





s 


0) 

C 


1 




m 


40% straight nitro- 
glycerine dynamite. 

60% straight nitro- 
glycerine dynamite. 

40% strength gelatine 
dynamite 

40% strength ^ am- 
monia dynamite. . . 

FFF black blasting 
powder (300 grs.). . 


273 
22.2 
50.8 
41.4 

49-7 


26.9 

34-6 
30 
3-8 

10.8 


0.0 

0.0 
0.0 
0.0 
0.0 


18.0 
23.2 

1.8 

31 

1.8 


0.4 

0.8 
0.8 
0.8 
0.6 


27.4 
19.2 
39-5 
45-5 
28.4 


41 

5-4 
8.7 


88.5 
128.9 
60.3 
65.6 
67.8 



BLASTING 239 

A further distinctive feature of gelatine dynamite, winning 
for it the advantage over ammonia dynamite for most tunnel 
work, consists in its practically waterproof quality, a condition 
largely due to the insolubility of the blasting gelatine which 
can be freely immersed in water with but Httle if any of it dis- 
solving. Ammonia dynamite, on the other hand, being hygro- 
scopic, has a great affinity for moisture and hence not only 
cannot be used in wet work (or even in damp work when it is 
necessary to spUt the original parafhned paper covering), but 
greater care must be used in selecting a dry place for storing it. 

Gelatine dynamite is somewhat less sensitive to direct shocks 
than other dynamites, and unUke them the sensitiveness does not 
increase with the strength; much stronger detonators must 
therefore be used even with the higher grades in order to insure 
complete detonation. This fact is often not sufficiently ap- 
preciated by practical mining men, many of whom are not 
aware of the greater ultimate economy obtainable if the more 
powerful, although somewhat higher-priced, detonators are used 
with gelatine dynamites. 

The strength of nitroglycerine dynamites as they are made 
to-day is generally rated according to the percentage of their 
nitroglycerine content, in spite of the fact that both the volume 
of gases and the temperature (and hence the disruptive force) 
are augmented somewhat by the combustion of the absorbent 
material. Although 40 per cent, is the strength most generally 
employed, they may be obtained in the following grades : 15, 17, 
20, 25, 30, 33, 35, 40, 45, 50, 60, 70, 75, and 80 per cent. In 
the ammonia dynamites a portion of the nitroglycerine is re- 
placed by ammonia nitrate, but, as will be seen from the table 
on page 237, the rated strength of this dynamite is nearly the 
sum of the percentages of these two constituents. Ammonia 
dynamite is prepared in the same grades as nitroglycerine 
dynamite, between 25 and 60 per cent. Owing to the strength 
of the blasting gelatine being greater than either of its constitu- 
ents, the rated strength of gelatine dynamite is somewhat greater 
than the percentage of its explosive element. The usual grades of 
this dynamite correspond to those of nitroglycerine dynamite 



240 MODERN TUNNELING 

between 2>5 and 80 per cent., but it may also be procured in 
'^loo per cent." strength. 

The proper grade for use at any particular tunnel must be 
determined solely by local conditions. Such widely divergent 
results are obtained at different locahties when using the same 
grade of explosive and in rock which, as far as can be deter- 
mined from its physical appearance and structure, is identical, 
that it is impossible to be dogmatic even with minute knowl- 
edge of local details. Generally speaking, however, a tough, 
close-grained, igneous rock will require a stronger explosive, 
while a sedimentary rock, or an igneous rock that has been 
altered and weathered, or perhaps shattered and broken, can 
be blasted just as effectively with a lower grade of dynamite. 
A notable example of the use of an extremely high-grade ex- 
plosive is that of the Roosevelt tunnel, where in the tough, 
close-grained. Pike's Peak granite "100 per cent." gelatine 
dynamite was required before satisfactory results were obtained. 
This is reported to have been the first "100 per cent." dynamite 
put to use in tunnel work. In all cases it is advisable to ex- 
periment at the beginning of the work with explosives of different 
strengths in order to determine which grade is best suited for 
the particular rock being penetrated, and it is, of course, obvious 
that similar experiments should be repeated whenever, owing 
perhaps to a change in the character of the rock, the dynamite 
used fails to give satisfactory results. 

The practice of loading the bottom portion of the hole with 
80 and even 100 per cent, dynamite and using 40 or 60 per cent, 
in the remainder is not now uncommon, especially in tunnels 
and adits in the Western States. It has the advantage of pro- 
ducing a greater disruptive force at the bottom of the hole, where 
such force is most needed, and at the same time it reduces some- 
what the cost of explosives, especially when an excessive amount 
of lower-grade dynamite had hitherto been required. There is 
entailed, of course, the trouble of handhng two different kinds 
of dynamite, not only in the heading but in the thawing-house 
as well. Although in some cases where this procedure was tried 
the same results might possibly be achieved by the use of shorter 



BLASTING 



241 



rounds, an alteration in the type of cut, or some other change in 
method, still it is a very useful practice, especially for exceed- 
ingly hard, tough rock. 

The following table shows the grades of dynamite employed 
at various tunnels: 



DYNAMITE USED AT VARIOUS TUNNELS 



Kind 



Strength 



Remarks 



Carter 

Catskill Aqueduct: 

Rondout 

Wallkill 

Moodna 

Central 

Gold Links 

Gunnison 

Laramie- Poudre . . . 



Lausanne 

Los Angeles Aqueduct ; 
Little Lake 



Grapevine 



Elizabeth Lake , 

Lucania 

Marshall-Russell . 

Mission 

Newhouse 



Nisqually , 
Rawley . . 



Raymond . . . 
Roosevelt . . . 
Siwatch .... 
Snake Creek 



Stilwell 

Strawberry . , 
Utah Metals 
Yak 



Gelatine 

Gelatine 
Gelatine 
Gelatine 
Gelatine 
Gelatine 
Gelatine 
Gelatine 

Gelatine 

Gelatine 

Ammonia 

Gelatine 
Gelatine 
Gelatine 
Gelatine 
Gelatine 

Gelatine 
Gelatine 

Gelatine 
Gelatine 
Gelatine 
Gelatine 

Gelatine 
Gelatine 
Gelatine 
Gelatine 



40 

60 
60 

75 
40 
40 
40 and 60 
60 

60 

40 

40 

40 

50 
40 and 80 
40 and 60 

40 

40 
40 and 60 

40 and 60 

40, 60 and 100 

40 

40 

40 

40 

40 and 60 

40 



Some 80% 



A small amount of 60% 
Mostly 60% 
Some 100% with the 
60% in cut holes 



Some 25% and some 

60% 
Some 60% and 75% 

gelatine 
Tried 60% & 70% also 

80% also 

100% with 40% in cut 
holes occasionally 

60% in cut holes and 
lifters 



Some 35% and some 
60% 



It is obviously impossible to make any set rule for the deter- 
mination of the proper amount of explosive to be employed in 
tunnel work, without special reference to given conditions. There 
are entirely too many variable factors, governed solely by local 
conditions, which control the fitness of quaHty and quantity, and 



242 MODERN TUNNELING 

which cannot be foreseen. Various writers have derived from 
theoretical considerations formulas for the calculation of the 
proper charge of explosive for a blast hole, but the application 
of these rules is limited to other types of blasting, such as quarry- 
ing or general mining, and they are not suited to the practical 
and actual conditions of tunnel work. For this, the determi- 
nation of the proper amount of explosive is often left to the 
judgment of the foreman in charge, who, if he be widely ex- 
perienced, can often produce excellent results; but the proper 
amount can best be ascertained by a series of experiments in 
which the effects produced by different quantities of explosive 
are studied and compared. 

It is very essential, however, that the charge of explosive 
be large enough. If it is too small and the cut-holes fail to break 
bottom, or the rest of the holes do not blast out their full share 
of rock, it will be necessary to reload the remaining portion of 
them; this procedure not only requires fully as much explosive 
as if the holes had been properly charged in the first place, 
but also occasions a loss of time and footage, both of which 
are most expensive. For this reason, in a number of tunnels, 
it was customary to load the cut-holes nearly to the collar. 
Although this is perhaps extreme, as far as insuring that the 
cut-holes break bottom is concerned, the extra dynamite helps 
to shatter the rock in finer fragments, thus making it easier 
for the shovelers to handle. Also, since no tamping is usually 
employed in such cases, a certain amount of the explosive prob- 
ably acts in that capacity and increases the efficiency of the 
remainder of the charge. The very common practice of loading 
the lifters entirely full has a very different object in view — 
that of throwing the major portion of the debris some distance 
away from the new face of the heading, thus making it easier 
for the drill-men to get their machines at work promptly, and 
by scattering the rock over a greater area the shovelers can 
attack it to better advantage. Such a practice is highly to be 
commended. 

Data as to the exact amount of explosive actually employed 
in practice are difficult to obtain, chiefly because at many places 



BLASTING 243 

an accurate record of powder consumption is not kept; but 
figures were secured wherever possible at the tunnels visited. At 
the Gunnison tunnel an average of nearly 30 pounds of 40 per 
cent, and 60 pounds of 60 per cent, gelatine dynamite were 
employed per round. This is equivalent to approximately 5.5 
pounds per cubic yard excavated. In driving the south heading of 
the Elizabeth Lake tunnel, the average for 1909 was 32.09 
pounds * of explosive per foot of tunnel, which is equivalent to 
6 pounds per cubic yard. This figure, however, includes the 
dynamite used in trimming, hence it is somew^hat higher than 
the amount actually needed in driving. At the Rondout Siphon, 
175 to 200 pounds per round were required to drive an average 
of 10 feet,t with a heading of approximately 120 square feet 
area — which is equivalent to 3.9 to 4.5 pounds per cubic yard 
of rock excavated. 

In advancing the heading of the Buffalo Water tunnel, 4.8 
pounds of 60 per cent, dynamite were required per cubic yard. 
At the Laramie-Poudre tunnel, the powder consumption per cubic 
yard for March, 191 1, was 3.9 pounds; for April, 4.7 pounds, and 
for May, 4.9 pounds. The average on the Little Lake Division 
of the Los Angeles Aqueduct for May, 191 1, was 4.5 pounds per 
cubic yard. At the Wallkill Siphon the average powder con- 
sumption per cubic yard ranged from 4.3 to 4.6 pounds. At 
the Yonkers Siphon the powder consumption was approximately 
4.5 pounds per cubic yard excavated. 

The figures for the explosive used in the Simplon and the 
Loetschberg tunnels are somewhat higher. At the Simplon 
tunnel the charge was 6.5 pounds per cubic yard,t while at 
the Loetschberg tunnel the charge per round to secure an average 
advance in the 6.5 by ten-foot heading of approximately 3.5 
feet was 53 to 57 pounds. § This is equivalent to 6.5 to 7 pounds 
per cubic yard. 

* Mines and Minerals, September, 1910, p. 102: "The Elizabeth Lake 
Tunnel," C. W. Aston. 

1; Engineering Record, January i, 1910, p. 26: "Progress on the Rondout 
Pressure Tunnel," J. P. Hogan. 

t Saunders, W. L., Trans. Am. Inst. Min. Eng., July, 191 1, p. 515. 

§ Saunders, W. L., loc. cit. 



244 



MODERN TUNNELING 



The usual means of firing blasting charges, especially in 
tunnels and adits in the Western States, is by the use of a safety 
fuse. The term safety fuse originated from the fact that when 
properly used under working conditions this fuse burns at a 
uniform rate and does not flash or explode, as was often the case 
with the means employed for igniting blasting charges previous 
to its invention; but the term is somewhat misleading, because 
this fuse is not, nor has it ever seriously been claimed to be, 
safe for use in gaseous coal mines. The fuse used for tunnel work 
is universally of the waterproof type, composed of a core of 
gunpowder surrounded by various layers of waterproofing ma- 
terial. In one sample, examined by the Bureau of Mines, "the 
core consists of a powder train and one white cotton thread; 
the inner covering consists of ten hemp threads; the inner- 
middle covering consists of five fine cotton threads impregnated 
with an asphaltic composition; the middle covering and the 
middle-outer covering each consists of a f^-inch cotton tape 
impregnated with an asphaltic composition, and the outer cov- 
ering consists of a f^-inch cotton tape covered with whiting. 
Each covering of tape is wrapped in reverse order." * 

In other samples the hemp threads of the inner covering 
are replaced by cotton threads impregnated with sodium siK- 
cate; the inner middle covering is often omitted; the asphalt 
composition of the middle covering is replaced by gutta percha; 
the middle outer covering is also omitted, and intervowen 
cotton threads are substituted for tape in the outer covering. 
The weight of powder in different types of waterproof fuse 
varies from 50 to 220 grains per foot, the majority of which 
is finely granulated, and will pass through a 60-mesh sieve. 

Under ordinary conditions a safety-fuse burns at a uniform 
rate, with a variation rarely greater than 10 per cent., fast or 
slow. In European countries the normal rate is approximately 
thirty seconds per foot. According to tests conducted by the 
Bureau of Mines on fourteen samples of triple tape fuse pur- 
chased for the Isthmian Canal the average rate was determined 



* United States Bureau of Mines, Technical Paper 7, p. 7. 



BLASTING 



245 







^^ ^^ ^^ 




>-i >-i rot^ lO OS 




00 t>. 00 t^ 00 t^ 




II II II II . II II 








M 


rorc^ ^ c^r^^ cot^^ ^. 


a 
6 

Pi 


^^d^-^.l £5t:"d*"^<=> [^idd^^.5 

^'^'^";;5,i >^^"{;5a >^'-5^5$ii 




fo"o "►-' "o 11 ^ o 00 vo >< 11 11 H^ o vo o_ 11 ^ 
^^^^^00^ ^^^^^«>.^ ^^^r.^^^ 






! 


Av. 

Max. = 
Min. = 
Range = 
Range fo 
Av. time 

Av. = 
Max. = 
Min. = 
Range = 
Range fo 
Time for 

Av. = 
Max. = 
Min. = 
Range = 
Range fo 
Av. time 






•a 
c 


^. ...... :^. .... c :...... - 


o 




U 






1 








CCOO t-^ '^ O '^OO M r^vO \D\D <X) ONOO fO I^^ rl- lO lO tJ- "tJ- C^ C4 


"* 0) vO 00 On^ 0) CS .^ 'd-oO '^ CO '^00 r^ lO HH CO -^ ^^vO vO cs ^ 




1 


w 




lo .^ r^ On OS r^oo r^vo vo o\^ lovo o\iop-hO o cocococO'^on 


S 


^ 




rn 


cOcocOcOcocOO O cocOcOcOcOcOcOO O O i-h m hh O O O^ 0\ 


H 








cj 


. On r^ lO (S I^VO )-i Tt- uo lOii^ONOOOOOi^CN'-''-' 


J 


C 


lO^i-i-i cOcOi-1 OMOCS) O COM lO^cOcOiO'^n lOiOHi w Tl-cO 


ID lo^o vo vd ^ 00 t^vo vij vb* vo to\o vo r^o r^oo » oo r^ w lovo 






l-(l—( t-HH^I-HP-HI— CHHI— (h-ll— It-I 








OS 


00'^000iOU000000000iO(^0000»OC oo 


ai^l 


„wOH-,w«r:hr^hHOMM!=.w)=.cOcOiOlO'^lOcOC':icO'* 




sr 


00 00 00 00 00 00 lO lOOO 000000000000 CN (N lOlOlOlOC^ <M <N (N 


C^(N (MC^nMCSCNMCJCNCl 


°3 


HI 01 CO '* lOVO t^OO On O 1-1 ri CO '* lOvO 1^00 OS O i-i 04 CO "* lO 


o 


H 


|_l-((-.MhHl-(l-<H^h-(H-.CN(SMCM(NCl 



246 MODERN TUNNELING 

as 26 seconds per foot for three-foot lengths and 24.5 per foot 
for fifty-foot lengths. This rate is much slower than that of 
the fuse commonly employed in Western tunnel work, forty to 
forty-five seconds per foot being the customary rate of burning 
for fuse used there, although these figures are not the results of 
tests. Such a test was made at the Strawberry tunnel, however, 
with the results shown in table on page 245. 

Experiments conducted by the Bureau of Mines * prove 
conclusively, however, that the normal rate of burning of fuse is 
greatly changed by a number of conditions. Excess of pressure 
greatly accelerates it, and if the gases are sufficiently confined 
the increase may be as great as 300 to 400 per cent. Although 
as great an increase as this would rarely be obtained in practice, 
the use of tamping which is too tightly packed or which is 
impervious to the escaping gases may produce sufficient pressure 
to increase greatly the rate at which the fuse burns. When fuse 
is exposed to low temperature for a short time the rate is slightly 
increased, but if it be stored at temperatures below freezing 
and handled before being warmed, cracks are apt to result in 
the waterproof composition which will permit the gas to escape, 
and thus, reducing the normal pressure, retard the speed of the 
fuse. Storage at high temperatures, however, causes a marked 
retardation which is apt to cause delayed shots and misfires, 
and fuse should, therefore, never be stored near boilers or other 
places where the temperature is high. Moisture seriously im- 
pairs the efficiency of fuse which should be carefully protected 
from it. Although the train of powder is covered with a water- 
proof covering throughout its length, the powder exposed at the 
end readily absorbs moisture and the cotton or hemp threads 
in the center act in the capacity of sponges, so that the fuse for 
a foot or so from the end may be impregnated with moisture. 
When the fuse is Hghted, this water is driven ahead of the fire 
in the form of steam and delays the burning of the fuse, and, if 
there is enough of it, sometimes becomes concentrated and 
extinguishes the fuse entirely. Although twisting and bending 

* Technical Paper No. 6. 



BLASTING 



247 



apparently have but little effect upon the rate of burning, 
mechanical injury, such as pounding or crushing by falling 
rock, and abrasion such as might result from the tamping 
stick when consoHdating the charge, greatly increase the rate. 
The results of these experiments show most conclusively that 
the greatest care should be taken in the storage and han- 
dling of fuse to prevent accidents from premature or delayed- 
explosions. 

Detonators or blasting caps consist of a copper cylinder 
closed at one end and about the diameter of an ordinary lead 
pencil, into which is packed some dry mercury fulminate and 
potassium chlorate. When used with a safety fuse, the end 
of the fuse is inserted in the open end of the copper cyhnder, 
which is then crimped around the fuse by the use of suitable 
pHers. Under no conditions 
should anything but the proper 
tool be used for this purpose, be- 
cause the fulminate of mercury is 
extremely sensitive to very shght 
shocks, and there is sufficient 
strength in a single detonator to 
produce disastrous results if dis- 
charged accidentally. In some 
tunnels, more especially those in 
the Eastern States, the detona- 
tors are ignited directly by an 
electric current. For this purpose, 
special electric detonators are re- 
quired in which the fuse is re- 
placed by two suitably insulated 
copper wires joined at the inside 
end by a bridge of fine platinum 
or other high-resistance wire 
capable of becoming incandes- 
cent during the passage of an 

electric current; these are inserted in an ordinary detonator 
into which some gun-cotton has previously been placed. Caps 



Gun Cotton or 

Mercury Pulminate 
(loose) 




Fig. 64. Section through an 
electric detonator. 



248 MODERN TUNNELING 

prepared in this manner are called electric detonators and may 
be secured from the manufacturers with wires of varying 
lengths, as required. 

Figure 64 shows the component parts of one of these 
detonators. 

The strength of detonators is determined by the weight of 
mercury fulminate they contain, and they are generally desig- 
nated as triple X, quadruple X, etc. 

The following table shows the weights of charge used in the 
different grades: 

WEIGHTS OF DETONATOR CHARGES 

Commercial Grades Weight of charge in grains 

3 X — or triple 8.3 

4 X — or quadruple 10 . o 

5 X — or quintuple 12.3 

6 X — or sextuple 15.4 

7 X — or No. 20 23 . 1 

8 X — or No. 30 ' 30 • 9 

WEIGHTS OF ELECTRIC DETONATOR CHARGES 

Commercial Grades Weight of charge in grains 

Single strength ....12.3 

Double strength 15.4 

Triple strength 23.1 

Quadruple strength 30.9 

The detonator chosen for blasting in tunnel work should be 
strong enough to produce complete detonation. With straight 
nitroglycerine dynamite 3 X caps were considered heavy enough, 
but with gelatine dynamite it is necessary to use much stronger 
ones because this dynamite is not nearly so sensitive (which 
makes it, of course, safer to handle). The jelly-like mass of 
the gelatine dynamite also has a tendency to retard the explosive 
wave as it passes along the bore-hole, and therefore requires a 
much stronger initial explosion to carry the wave with the 
same force through the entire length of the charge. The leading 
manufacturers all recommend nothing weaker than 6 X caps 



BLASTING 249 

for gelatine dynamite. Although 5 X caps have given results 
which were thought to be sufficiently satisfactory at some 
tunnels, at others, where a change was made to those of greater 
strength, the universal experience has been that the better 
results more than warranted the change, the common report 
being that "it pays." It is, therefore, here recommended that 
nothing weaker than 6 X detonators (or double-strength electric 
detonators) be used with gelatine dynamite, which is practically 
the only kind employed in tunnel work. In addition to the 
more effective results produced by the higher-strength caps, the 
composition of the gases is greatly changed w^hen detonation 
is not complete, and unsuspected and dangerous constituents 
may result. As we have seen, with complete detonation the 
gases are mainly carbon dioxide and nitrogen, with, perhaps, a 
small amount of carbon monoxide. With incomplete detonation 
a much greater percentage of dangerous carbon monoxide is 
formed from the nitroglycerine, and, in addition, the toxic 
peroxides of nitrogen are produced in larger or smaller amounts, 
according to varying degrees of completeness of the reaction. 

LOADING 

There has been much discussion lately regarding the proper 
position for the primer (as the particular cartridge of dynamite 
containing the detonator is called) when loading a blast hole; 
some arguing that it should be the last cartridge to be placed 
in position, while others claim the only proper place for it is 
at or near the bottom of the hole. One of the more common 
arguments for placing it at the top instead of the bottom of the 
hole is the fact that by so doing one removes the danger of 
igniting the dynamite from the side-spitting of the fuse, in which 
case not only is the full efficiency of the explosive not obtained, 
but the resulting gases are much more virulent and dangerous. 
For it is obvious that when the fire in the fuse is compelled to 
travel past the full length of the charge, the danger of the flame 
bursting through the waterproof covering and igniting the dyna- 
mite is a rather serious matter. We are informed, however, by 
an expert connected with one of the leading explosives manufac- 



250 MODERN TUNNELING 

turing companies, that gelatine dynamites (which, as we have 
seen, are the kind generally used in tunneling) are less liable 
to be deflagrated in this manner than any of the others. The 
objection (which, however, is not applicable when electric de- 
tonators are used) is worthy of serious consideration when safety 
fuse is employed. 

A second argument in favor of placing the cartridge last is 
the fact that the dynamite charge is much more apt to be packed 
firmly, thus eliminating air spaces which decrease the effective- 
ness of the explosive. For when the primer is the first or the 
second cartridge in the hole, the remaining cartridges, and 
especially the one immediately following, cannot properly be 
pressed in place with safety, and air spaces are quite Hkely to 
be left. This, of course, applies equally to charges detonated 
by safety fuse or electricity. 

A third argument, and one that seems to have been over- 
looked in the recent discussion, is the fact that the detonation 
of a charge of dynamite in a bore-hole takes place in a series 
of steps which follow one another with almost inconceivable 
rapidity, but which are nevertheless distinct. The first of 
these is the explosion of the cap, which in turn detonates the 
dynamite in the primer and causes what may be termed the 
primary explosion, which in turn is communicated to the re- 
mainder of the charge. Although, by employing a strong cap 
the amount of dynamite detonated in the primary explosion 
can be greatly increased, it can never be large enough to disrupt 
the rock completely, the greater force of the secondary explosion 
being required for this purpose. If, then, the cartridge contain- 
ing the detonator is placed at the bottom of the hole and fired, 
the primary explosion consumes the dynamite ineffectually at 
the bottom of the hole where the full force of the blast should 
be used; consequently, there is much greater danger of losing 
the last eight or ten inches of the round, with a consequent 
decrease in daily advance. It is also claimed that in placing the 
primer at the bottom, the explosion of the detonator tends to 
force a certain amount of the charge from the hole; this, how- 
ever, is debatable. But if the primer is placed at the top, the 



BLASTING 251 

primary explosion does not destroy explosive that is essential 
and the full strength is developed from the remaining portion of 
the explosive, except in so far as it is influenced by the hindrance 
to the explosive wave caused by the use of gelatine dynamite 
previously referred to. And again, by placing the primer at the 
top, during the primary explosion a certain amount of pressure 
is developed and the remainder of the charge is, therefore, deto- 
nated under that greater pressure, hence its effectiveness is 
increased. This applies particularly where tamping is employed, 
and it requires only two or three inches of clay tamping to pro- 
duce the results. If clay is not used, an extra stick of dynamite 
placed on top of the primer, which acts partly in the same 
capacity, is of great assistance. 

On the other hand, it is claimed that when the primer is 
placed on top of the charge the collar of the hole is apt to be 
knocked off by the explosion of a neighboring charge. There is 
some question as to whether this really would happen, but if it 
did it would be a very strong indication either that the hole 
was misplaced or that it was too heavily loaded; for, as some 
one has said, "Certainly the collar of a hole is no place for 
dynamite." And as to the objection that when the primer is 
placed at the top the fuse is Kable to be torn out by flying rocks, 
the remedy is a very simple one — that of coiHng the fuse care- 
fully close up to the hole. And finally, if the wave does not 
travel with enough force to the bottom of the hole, the matter 
can be remedied by the use of a strong detonator, or by employ- 
ing a higher grade of explosive, which would have the double 
effect of producing a greater primary explosion and of lessening 
the length of the charge, since less explosive would be required. 

It is clearly recognized by the authors that, in some sec- 
tions of the country at least, the practical miners are accustomed 
to place the primer at the bottom. But it does not necessarily 
follow that a practice is correct because the miners so consider 
it, for many of them also think that dynamite exerts a greater 
influence downward than in any other direction. Therefore in 
view of the several considerations outHned above, it would 
appear that the primer should be placed near the top of the charge. 



252 MODERN TUNNELING 

The use of tamping in tunnel work is also a mooted question. 
Where low explosives, such as blasting powder having a slow rate 
of explosion, are employed, tamping is of course absolutely essen- 
tial in order to confine the gases long enough for their full strength 
to become effective. But with dynamite whose detonation is 
extremely rapid, almost instantaneous, it is beheved by many 
persons that tamping is not required, and this behef seems to 
be warranted by the actual experience that good results can 
be obtained without its use. A possible explanation for this is 
the fact that in tunnel work the holes are generally overloaded, 
and hence the pressure produced by the extra few inches of dyna- 
mite charge tends to confine the gases generated by the remain- 
ing and effective part of the charge, which is of course also the 
function of tamping. Another probable reason is that the inertia 
of the column of air in the bore-hole acts as a partial substitute 
for tamping of some more solid material. This can be demon- 
strated by exploding dynamite lying uncovered upon some 
flat surface in the open, and it is this fact, doubtless, that has 
given rise to the belief that dynamite exerts more force down- 
ward than in any other direction. It is unanimously admitted, 
however, by experts who have studied the subject, that better 
results can be secured from any properly loaded hole when more 
substantial tamping is employed. The amount required depends, 
of course, upon the rate of detonation of the explosive. With 
black blasting powder it may be necessary to fill nearly all the 
remaining portion of the hole in order that the tamping may not 
be forced out before the reaction is complete and the full strength 
of the gases produced; but with ordinary charges of gelatine 
dynamite from two to six inches of well-packed clay will in most 
cases be fully sufficient. 

The use of tamping in tunnel work has several disadvantages 
which, in the opinion of many, if indeed not a majority, of tunnel 
men, more than counterbalance any gain in efficiency of explosive 
from its use. In the first place, it causes delay in loading the holes 
at a time when every minute is precious. Again, the majority of 
miners and especially those in the Western States, are strongly 
biased against it, and any one who has tried to overcome one of 



I 



BLASTING 253 

their prejudices will appreciate the difficulty that would be expe- 
rienced in getting them to use the tamping. While, of course, if 
tamping were absolutely essential to good results, mere prejudice 
on the part of any one should not be allowed to stand in the 
way of its adoption, still, as this is not the case, the wishes of 
the miners are usually deferred to. But a more serious disadvan- 
tage of the use of clay or similar material for tamping is the 
danger attendant upon its removal in case of a missed hole. This 
is a proHfic source of accident. But if the tamping consists of 
an extra stick of dynamite, as is usually the case in tunnel work, 
the simple insertion of a primer on top of the unexploded charge 
is all that is needed to prepare the hole for re-firing. For these 
reasons, then, although tamping is essential in a bore-hole that 
is not overloaded, for tunnel work in which it is customary to 
use more rather than less "powder" than is required, it is not 
so necessary that clay, sand, or similar tamping be employed. 

Among other things to be considered in connection with the 
loading of a blast hole is the necessity of having the dynamite 
properly thawed. This is required, not only by due regard for 
the safety of the men (which alone should be more than sufficient) , 
but also because frozen dynamite cannot be properly packed in 
the hole, and air spaces cannot, therefore, be avoided, nor is the 
full force of frozen dynamite developed upon detonation, hence 
there is a decided loss in effectiveness. It is also very desir- 
able that the cartridges correspond as closely as possible in diam- 
eter to the size of the drill hole, and that the paper shall be slit 
(carefully, of course) along the side with a sharp knife just before 
they are placed in the hole. This enables the explosive to con- 
form to any irregularities in the shape of the hole. The position 
of the detonator in the priming cartridge also deserves attention. 
Experiments have shown that the maximum force from a deto- 
nator is developed in the direction of its length. For this reason 
the detonator should be inserted into the end of the cartridge 
and not obHquely in one side, as is often the case in tunnel 
practice. Nor should the fuse project into or be laced through 
the cartridge because of danger of setting fire to the cartridge, 
instead of detonating it properly with the cap. 



254 MODERN TUNNELING 

FIRING 

When the number of holes to be fired is large, the work of 
lighting the fuses is generally done by two men, but when there 
are but few holes in the round, one man is sufficient. When two 
men do this work it is customary for each man to light the fuse 
of a corresponding hole (for example, opposite cut holes, etc.), at 
the same time, each calling out the hole as he lights it. The actual 
ignition of the fuse (which should be closely coiled and the free end 
split for one-half to three-fourths of an inch to expose the powder 
train) is accomphshed in various ways. At some places a candle 
is used, and at others an acetylene lamp. The much better prac- 
tice, however, is to use a "spitter," as it is called, consisting of a 
short piece of fuse which has been slashed and partially severed 
at regular intervals of perhaps one-half of an inch, and the powder 
train exposed. When the end of such a spitter is ignited the fire 
travels along it and as it reaches one of the cuts it spits violently 
out of the side, which if directed toward a fuse is almost certain 
to ignite it properly. Each fuse should be ignited separately, 
instead of bunching several of them, and attempting to ignite 
them all at once, as is unfortunately sometimes done. When it 
is necessary to protect the ends of the fuse from water by cover- 
ing it with anything convenient, an empty powder box is fre- 
quently employed. 

In extremely wet tunnels it is sometimes necessary to use a 
fuse igniter. One form of igniter that has given excellent results 
at a number of places where tried consists of a short cyHnder 
of celluloid of the same diameter as the outside of standard 
fuse, which is closed at one end, and contains a small amount of 
gunpowder or some similar explosive substance. The other end 
is slipped over the free end of the fuse which, instead of being 
split, is cut square, and the igniter fits the fuse tightly enough 
to be held in place by friction. When being Hghted the igniter 
is, of course, protected from any falling water, and the celluloid 
is set on fire by a candle or some other flame; since it is unaf- 
fected by mere dampness, it burns until the powder charge is 
reached, when a flash takes place which seldom fails to start the 



BLASTING 255 

fuse. These igniters are not expensive, and are exceedingly 
useful in wet work. 

When ordinary electric detonators are employed, the only 
operations required are those of connecting the wires and passing 
a current through them by closing an electric-light circuit, or 
by generating a current in a so-called '' battery," which consists 
of a hand-operated magneto or dynamo. In this case, all the 
holes so connected are exploded simultaneously, and this is the 
chief and most serious disadvantage of electric firing for tunnel 
work. As we have seen, the blasting in tunnel headings, to 
be effective, must take place in several steps; the cuts first, 
followed by the rehevers, backs, sides, and hfters. Therefore, 
with electric blasting, although it has the advantage of shooting 
the cuts simultaneously, it is necessary for some one to return 
to the heading and connect up the wires leading to the charges 
in the holes to be fired in each of the succeeding steps; and as 
it always requires a certain amount of time in order to permit 
the smoke to clear, and oftentimes no little shoveling is required 
to uncover wires which have been buried by a previous round, 
it takes much longer to blast a round in this manner. 

Manufacturers of blasting supplies are trying to perfect a 
delay- action detonator, in order to overcome this defect. This 
resembles ordinary electric detonators, except that the platinum 
bridge does not ignite the mercury fulminate directly, but sets 
fire to a short train of gunpowder inside of the cap, which 
requires an appreciable, although short time, in burning before 
it reaches the detonating portion. By making the powder train 
of two different lengths, two delays are obtained which, if used 
in connection with a detonator not containing a powder train, 
enables the blasting to be performed in three stages from a single 
connection of the wires and from but one closure of an electric 
current. When using these devices in tunnel work an instan- 
taneous detonator is usually placed in the cut holes, a ''first 
delay" in the relievers, and the ''second delay" in the remaining 
holes. It is unfortunate that these detonators have not as yet 
been perfected for more than two delays, and this has un- 
doubtedly prevented their more extensive use for blasting tun- 



256 MODERN TUNNELING 

nel headings. For this work^ three stages will hardly give satis- 
factory results, because a fourth stage is essential for the hfters, 
whose function it is to throw the material broken by the other 
holes from the immediate front of the new face; and with the 
horizontal-bar mounting a fifth step is also desirable in order to 
permit one lifter to go off after the others and throw the material 
away from the side of the tunnel where the capstan end of the 
bar is to be placed, thus to afford plenty of room for the operation 
of the jack bar and permit it to be screwed tightly in place. 

There is, however, riow upon the market an electric fuse 
which will permit of the blasting being conducted in almost any 
number of steps that may be required. It consists, as does the 
ordinary electric detonator, of a platinum wire bridge enclosed 
in a metal cylinder by a waterproof composition. In the other 
end of the cylinder (which, instead of being closed and containing 
mercury fulminate, is left open) a short section of ordinary 
safety fuse is inserted, crimped in place, and the joint water- 
proofed. After an ordinary blasting detonator has been placed 
upon the other end of this piece of fuse and an electric current 
is passed through the copper wires leading to the platinum 
bridge, the fuse takes fire and burns until it ignites the detona- 
tor. By cutting off different lengths from these pieces of fuse 
before inserting them in the blasting caps, any desired number 
of delays may be obtained from one connection of the wires and 
one closure of the electric current. This device, therefore, 
overcomes the one great disadvantage of electric firing. 

Chief among the advantages of electric firing is the certainty 
of detonating all of the cut-holes simultaneously. Although, of 
course, if two holes are connected they will explode as one, it is 
impossible to make several pairs of cut-holes, in a wedge cut, 
for example, explode together when fuse firing is employed. 
There will always be enough variation in the rate of burning 
of the fuse to prevent it, no matter how exactly the lengths of 
the fuses are cut. But when the cut-holes are detonated simul- 
taneously, as can be done with electric firing, each can assist 
the other with a resulting increased effectiveness from the 
explosive. It is, of course, true that even with electric delay- 



BLASTING 257 

action detonations, holes fired on the first and second delay can- 
not be made to detonate absolutely simultaneously, and even 
less so with the electric fuse just described; but this is not so 
essential, since the work of the succeeding holes does not approx- 
imate that of the cuts. 

Another advantage is the absence of smoke and dangerous 
gases caused by the burning of fuse. A large percentage of these 
gases is carbon monoxide, as is shown by the following analysis 
of gases obtained from burning fuse.* 

ANALYSIS OF GASES PRODUCED BY BURNING OF FUSE 

(A. L. Hyde, Analyst) 

Hydrogen sulphide 0.8 

Carbon dioxide 32.7 

Oxygen 1.4 

Carbon monoxide 23.4 

Hydrocarbons 4.1 

Nitrogen 23 . 8 

Hydrogen . v-^-T-rrr 13.8 

100. o 
STORING 

The place used for the storage of explosives should be sub- 
stantially constructed, well ventilated, protected as much as 
possible from fire or lightning, and should be kept locked to 
prevent the entrance of children or irresponsible persons. At 
mines or quarries the ideal magazine is, of course, one of cement 
or of brick, but at most tunnels where the work is usually of a 
more or less temporary character, the cost of such a building is 
not always justified, and the dynamite is stored usually in a 
short drift in the side of the hill or in a log house. Where neither 
of these can be obtained, a frame house will answer the purpose, 
although of course not so well. But when it is used, it should 
always be covered with corrugated iron or some similar fireproof 
material, and care should be taken to remove any small sticks 

* Bureau of Mines, Technical Paper 6. 



258 MODERN TUNNELING 

and grass from immediately around it. Where considerable 
amounts are to be stored, the magazine should be located at 
some distance from the rest of the work, but in any case the 
powder should not be kept near enough to the tunnel buildings 
to cause serious damage to them or to the persons working in 
them in the event of an accidental explosion. Obviously, dyna- 
mite should not be stored at all near a dwelling. 

More than one kind of explosive, as, for example, black blasting 
powder and dynamite, should not be stored together, but there 
is no particular objection to the storage of different grades of the 
same kind of dynamite in the same building, except the possibihty 
of confusion which might result from such a practice. Detona- 
tors, either plain or electric, and fuse should under no circum- 
stances be stored in the same building with dynamite, nor 
should the operation of placing caps on safety fuse be conducted 
at or near the magazine or thaw-house. Tools should never be 
permitted inside of the magazine, nor should the boxes of dyna- 
mite be opened there. The floor of the magazine should always 
be constructed of wood, and it should always be kept free from 
grit and dirt. 

THAWING 

Most dynamite freezes at a temperature of 45° to 50° F., and 
it is therefore necessary to thaw it before it can be used. In 
tunnel work this is generally accomplished by spreading it out 
on shelves in a warm room or small building, separate and pref- 
erably somewhat removed from the main magazine. Where the 
power for the tunnel work is derived from a steam plant, the 
waste steam is very often used to heat the thaw-house. In this 
case, however, it is very essential that the coils be boxed or 
screened in such a way that it will be impossible for a stick of 
dynamite to fall upon the pipe, for, becoming ignited from the 
heat, a serious explosion might result. Nor should the pipes 
be so placed that any nitroglycerine exuding from the cartridges 
can fall upon them. Since the thaw-houses are generally insu- 
lated from the cold by having double walls or by banking earth 
high against the sides (and hence a great deal of heat is not 



BLASTING 259 

required to keep them warm), where electricity is available, a 
cluster of incandescent bulbs is often used for this purpose with 
good results. At other tunnels a special heater was observed, 
which was composed of one or more coils of iron or other high- 
resistance wire stretched between insulators on a suitable frame- 
work, usually of wood. When a heater of this type is employed 
it is much more essential that it be protected from the danger 
of a stick of dynamite lodging upon the wires because they are 
generally much hotter than steam coils (a red glow being not 
uncommon), and hence there is much greater danger of explosion 
from this source. 

At one of the tunnels visited, however, where otherwise the 
conditions from the viewpoint of safety were excellent, an 
unprotected heater of this type was employed, and when comment 
was made upon the fact that there was no protection, it was 
stated that this condition was intentional. The reason given for 
such a course was that any person entering the thaw-house was 
supposed to turn off the current by means of a switch provided 
for that purpose, and that the knowledge that the coil was not 
protected would make the men more careful in seeing that this 
was done. Such reasoning is all right as far as it goes, but it 
does not provide for the contingency of a stick of powder falhng 
off the shelves when no one is in the building (although it is 
granted that this is not so hkely to happen as the other); nor, 
since the wires do not cool off instantly, is it safe in the thaw- 
house for some Httle time even after the wires have been dis- 
connected. Taken in connection with the fact that this par- 
ticular thaw-house was but a short distance from the tunnel 
portal, that it had no lock, and that all timber and other tunnel 
supplies had to be hauled past it, the situation should have been 
marked, in the language of insurance, ''extra hazardous." It is, 
indeed, truly marvelous that it did not occasion some accident 
during the period of its use. Needless to remark, such a thaw- 
house and means of heating it are decidedly to be avoided. 



CHAPTER XIII 
METHODS OF MUCKING 

NUMBER OF MEN 

The number of men in the crew which removes the rock 
broken in blasting exerts a very important influence upon the 
speed at which the tunnel can be advanced. Where the vertical 
column or the drill carriage is employed and the remainder of 
the work cannot proceed until the heading is cleared, every 
minute saved at this work can be transmuted directly into 
progress; and while, with the horizontal-bar system, nearly all 
of the mucking is done simultaneously with the drilling and 
the heading can ordinarily be cleared by the time the drillers 
have finished the upper round of holes, still if the crew of shov- 
elers is not large enough to accomplish this promptly, the delay 
is fully as serious. In any event, it is very essential for rapid prog- 
ress that the muck be removed as speedily as possible, as there 
are always a great number of little things to be done by the 
shovelers, even after the main work of loading the debris has 
been accomplished, for which there cannot be too much reserve 
time. Further, it is obvious that the removal of the muck in 
the shortest space can be accomplished only by a nice adjust- 
ment to conditions and the employment of the exact number of 
laborers proper for the purpose ; for it must be remembered that 
the space in the tunnel heading is most restricted, and if too many 
men attempt to work there simultaneously, they will seriously 
interfere with one another, more than offsetting any possible 
gain from the employment of the extra men, while if too few men 
are at work it will be impossible for them to remove the debris 
in the time allowable. An analysis of the most satisfactory prac- 
tice at a number of tunnels shows that, under the conditions 
which prevail in the heading, a man shovehng requires from 
two and a half to three feet of floor space. That is, for a tunnel 
ten feet wide, not more than four shovelers should be used 

260 



METHODS OF MUCKING 261 

simultaneously, while not more than two men can work to advan- 
tage side by side in a six-foot heading. In addition to these, how- 
ever, it is very desirable to have a man or two at work picking 
down the rock pile in front of the shovelers, loosening boulders, 
assisting in the handling of the cars, or doing any of the many 
other things that make for speed in loading the muck. Accord- 
ingly, at tunnels from six to ten feet in width, the proper number 
of men in the mucking crew ranges from three to eight. 

At the Loetschberg and other of the European tunnels two 
sets of muckers were employed, one of which would rest while 
the other was engaged in loading the car. This course was 
thought to be conducive to greater speed, because the men could 
work much harder for the few minutes it took to load a car if 
they had an equal time to rest during the loading of the next 
one. There is but little if any doubt that this is true or that 
the heading can be cleared sooner when such a method is used, 
but because of the higher cost of labor in this country, especially 
in the Western States, it is greatly to be questioned whether the 
gain would be sufficient to make such procedure profitable. At 
the Loetschberg tunnel the shovelers received a daily wage of 
80 cents * as compared with the $3 or $3.50 for like work in the 
western part of the United States, so that a double crew of but 
five shovelers (similar to those of the Loetschberg tunnel) would 
entail in this country an extra cost of from $15 to $17.50 per 
shift, as compared with $4 in Europe. Since the advance per 
shift in America rarely exceeds 7.5 feet, the extra cost of the 
double-crew system would amount to at least $2 per foot of tun- 
nel driven. This would be justified only if it obviated a corre- 
sponding burden of delay, although even in that event the ques- 
tion could properly be raised whether a change or adjustment 
in some other phase of the work was not the better solution and 
desideratum. 

POSITIONS OF WORKING 

The advantage of giving the men a rest from the grind of 
steady shoveling can be obtained, however, without the necessity 

* Saundero, W. L.: Bull. A. I. M. E., July, 191 1, p. 532. 



262 MODERN TUNNELING 

of extra laborers, by changing their positions regularly, according 
to the system in use at several of the tunnels visited while secur- 
ing the material for this book. At the Laramie-Poudre tunnel, 
where one of the best examples of this method was observed, the 
six muckers worked according to the following cycle of opera- 
tions: As soon as a car (i) was filled with waste, two shovelers, 
who will be designated as A and B, took it at once to the rear, 
while two other shovelers, C and D, jumped to an empty car 
(2) near by (which had previously been thrown off the track on 
its side) , set it upright on the track, and pushed it into a position 
to be filled. In the mean time, the remaining men, E and F, 
stopped picking down the rock pile, took the shovels left by A and 
B, and started at once to assist C and D in filling car 2. Another 
car (3) was then brought up by A and B as near as possible to 
the car (2) being filled, and thrown off the track on its side in 
the position formerly occupied by the second car. These men 
then picked down the rock pile for the other four during the 
remainder of the time consumed in loading car 2. When filled, 
this car was removed by C and D, while E and F set up the third 
car and filled it with the assistance of A and B . The fourth empty 
car was meanwhile brought up by C and D, who then took their 
turn at picking down, and the cycle was completed when E and 
F took the third loaded car to the rear, returning with another 
empty and then resumed their original position on the muck 
pile. It will be seen that by this method every man spent at 
least one-third of the time in tramming or picking down the rock 
pile, either of which was easier work than that of shoveling and 
amounted virtually to a rest which, although perhaps not so 
complete as if no work at all had been done during that period, 
was still sufficient to relieve greatly the hard monotony of 
shovehng. 

The regularity and mechanical exactness of procedure with 
this system are still more important advantages. Each man soon 
learns precisely what is expected of him for each step of the 
operation, and hence there is absolutely no confusion, no lost 
motion. There is rarely any occasion for the foreman to give 
an order to the men except under unusual circumstances, and in 



METHODS OF MUCKING 263 

consequence he does not acquire the habit of shouting at the 
men constantly, an unfortunate phase of this work only too 
noticeable at some of the tunnels visited; nor, on the other hand, 
do they form the time-wasteful habit of running to him for 
guidance at every minor contingency that arises. The statement 
that the httle things make for success is not claimed as original, 
but it can nowhere apply better than in planning the utmost 
work attainable in the limited space of a tunnel heading; indeed, 
this seeming detail of eliminated friction and confusion warrants 
and deserves the most serious consideration. 

In addition to advantages in organization, the speed attain- 
able with this method leaves little, if indeed anything, to be de- 
sired. Cars of 1 6 cubic feet capacity were filled at the Laramie- 
Poudre tunnel ordinarily in three or four minutes, and on one 
occasion (which, however, was somewhat exceptional, as the 
men realized that they were being timed) but one minute and 
thirty seconds were needed. At the Rawley tunnel, w^here a 
similar system w^as used with but four muckers, twenty-five cars 
having a capacity of 1 7 cubic feet were filled in exactly two hours, 
and on a different shift twenty cars were loaded in one hour and 
forty-five minutes. These figures are from an accurately timed 
record kept by one of the authors. The usual time required for 
mucking at the Rawley tunnel is not far from the average of 
these figures (which also include all ordinary delay incident 
to making the cars up into trains), a value somewhat less than 
six minutes per cubic yard of rock loaded. This does not suffer 
by comparison with the Loetschberg tunnel, where five minutes 
were required to fill a cubic-meter car (35.5 cubic feet) * by a 
crew of ten men, with an extra minute to remove it when full 
and replace it with an empty one. 

HANDLING CARS 

The method of handling the tunnel cars is still another detail 
of consequence in the operation of mucking. One of the most 
common arrangements is to have them trammed from the face 

* Saunders, W. L.: Bull. A. I. M. E., July, 191 1, p. 535. 



264 MODERN TUNNELING 

by hand to a siding or switch where they are made up into trains 
and hauled to the portal by whatever means are provided for 
that purpose. This system, however, possesses some disadvan- 
tages. The switch must be moved frequently at no Httle expense 
and trouble in order to keep pace with the tunnel advance or 
else it will soon be so far from the face that it is practically worth- 
less. There is considerable loss of time while the loaded cars are 
being removed and the empty ones are being brought to the face, 
which it is impossible to avoid; even though every effort be 
made to reduce this time to the minimum, the switch cannot 
well be located nearer than loo feet from the face, while in prac- 
tice 300 to 500 feet is more apt to be the actual distance. More- 
over, the full car must be taken usually by hand the entire dis- 
tance to the switch before the ''empty" can pass it; when this 
system is employed, heavy cars, almost without exception, are 
used (for reasons we shall show later) , and, on this account, to 
move them any distance by hand entails a heavy drain upon 
the exertions of the mucking crew. 

At some tunnels this difficulty was obviated by extending 
two tracks all the way to the face and loading cars on each one 
alternately. Even this is not entirely satisfactory, because it 
requires the extra labor and trouble of laying two tracks instead 
of one, which must be done after the tunnel is cleared of debris 
and before the new round is fired, and is therefore very apt to 
cause a serious delay in the whole work, especially if the shovelers 
are a little late in clearing the heading. In addition, the need 
for keeping the switch as close as possible to the face is not so 
apparent with this method as with the first, and hence this most 
necessary work is apt to be neglected. In that event a large 
amount of time will be wasted in the course of a shift by the 
men tramming the cars an extra distance. And, of course, it 
only partially obviates the danger of derailments to the cars in 
crossing the switches, which is often a notable cause of lost 
time and trouble. 

At one tunnel the necessity for a double track was avoided 
by covering the entire floor of the heading with steel plates for 
about thirty or forty feet back from the face. The cars to be 



I 



METHODS OF MUCKING 265 

loaded could easily be jumped from the track on to the first of 
these plates and rolled as near the rock pile as necessary, and 
when one car was full an empty one could be shunted around it 
without difficulty and placed in position for loading while the 
full one was being rolled back upon the track and trammed to the 
siding when the trains were made up. Such a method is simple 
and efTective, and except for the work of moving the siding ahead 
requires but httle extra labor; most of the plates are needed in 
any event for the men to shovel from, so that the work of adding 
one or two more would scarcely be noticed. This procedure is 
recommended where for some reason it is necessary to employ 
cars of large capacity. 

But in most cases, as was pointed out in the section on 
haulage equipment (see page 163), it is much better to use cars 
of smaller capacity; then the empty ones are tipped off the track 
to allow the full ones to pass and can be righted when needed 
and placed back easily by two men, thus avoiding all the com- 
plications and extra work arising from the use of a siding or 
switch. The smaller cars are also easier to load, for since they 
do not occupy so much space in the tunnel heading there is more 
room for the shovelers to work; also, the sides of the smaller cars 
being low^r, each shovelful of rock does not have to be Hfted so 
high in order to get it into the car, saving both time and energy. 
They are likewise easier to handle in case of a derailment, and 
since fewer men are required for tramming them out of the head- 
ing when full, a larger percentage of the time of the shoveling 
crew can be spent in the actual process of loading. 

When the smaller cars are used, however, the work of handling 
them must be thoroughly systematized in order to prevent waste 
of time through avoidable delays. Although similar to that in 
use at a number of the tunnels examined, the system employed 
at the Rawley tunnel was perhaps more carefully worked out 
in all the details than were any of the others. Upon arrival at 
the heading, the empty cars were pulled as near as possible to 
the full cars waiting to be removed, which at this juncture 
ordinarily stood on the track some 75 or 100 feet from the face 
of the tunnel. The mule was then detached from the empty 



266 MODERN TUNNELING 

''trip" and used to pull the full cars back to the one being loaded, 
usually the last one of the previous empty trip; or if they had all 
been loaded the full cars were pulled back as near the face as 
possible. The empty cars were then hauled up to the full ones 
and tipped off the track on their sides out of the way. All of 
this work was performed by the mule-driver alone, except when 
the shovelers had completed the loading of the empty cars, in 
which case they assisted wherever possible in order to expedite 
matters. After seeing that the cars of the full trip were properly 
coupled up, the driver then started with them for the dump 
and the muckers took the two empty cars nearest the portal, set 
them on the track, and trammed them to the face where one car 
was again tipped off on its side while the other was being loaded. 
Unless the mule-driver was delayed in getting to the heading so 
that he did not arrive before all of the cars of the previous trip 
were filled (an event not of frequent occurrence, however), 
the operation of getting the loaded trip out of the heading and 
an empty car again in position to be loaded, rarely occupied more 
than from three to five minutes. The remainder of the cycle was 
similar to that just described for the Laramie-Poudre tunnel, 
each full car being trammed a short distance beyond the last one 
of the empty trip, which was then taken up to the face and 
thrown on its side ready for use without delay when 
needed. 

To recapitulate, then, the chief advantages of this system 
are: (i) it does away with a switch near the heading; (2) the 
cars do not have to be trammed any great distance by 
hand — only a little more than the length of one trip — and the 
distance is constant and does not vary with the tunnel advance; 
(3) the minimum time is consumed in getting the full car out 
of the way and replacing it with an empty one, and (4) very 
little time is lost in making up the trains to be hauled to the 
dump. It cannot of course be used satisfactorily unless the 
cars are small enough to be handled easily by two men, but this is 
a matter which can be provided for in purchasing the equip- 
ment and, as has been shown, the smaller car has other ad- 
vantages which make it very desirable for tunnel work. A 



METHODS OF MUCKING 267 

system similar to the one outlined, modified of course to fit 
local conditions, is highly recommended for future tunnel work. 

USE OF STEEL PLATES 

The use of steel floor plates from which to shovel rock broken 
by the blast has become so general that mention of this feature 
of mucking should hardly be necessary. The authors were 
much surprised, however, to find at one or two tunnels, where 
otherwise there was Httle left to be desired in the fine of organiza- 
tion and equipment, that the muck was being shoveled without 
the use of plates. Even the most cursory study of this work, 
noting the efforts of the men in pushing the shovels into the rock- 
pile along the uneven surface of the bottom of the tunnel and 
comparing the time required to load a car with the results at 
other tunnels where steel sheets were in use, soon made it evident 
that large quantities of both energy and time were being wasted 
needlessly. 

At one tunnel the plates were not used because it was neces- 
sary to excavate the floor on a curve instead of making it flat, 
as is usually the case, though even here plates could have been 
employed by leaving a portion of the waste material in the 
bottom of the tunnel to form a flat surface upon which the 
sheets might have been placed. Upon inquiry at another tunnel 
the following reasons were given for their non-use: (i) The 
muck was so sticky that it would not be at ah easier to shovel 
from the plates than from the rock-pile; (2) it was impossible to 
prevent the sheets from becoming bent, twisted, and jumbled 
up with the muck when the holes in the bench were blasted; and, 
(3) it was a great deal of trouble to lay them in position before 
blasting and to handle them during the work of mucking. 

Now, while it should be admitted in all candor that the 
stickiness of the muck in this instance made it difiicult to handle 
under any conditions, there is no good reason to suppose that 
shoveling from a plate would have been more arduous than from 
the pile — quite the reverse. The second objection is somewhat 
more serious; for it is true, especially with heavy blasts, that 
the sheets are sometimes caught up and twisted by the explo- 



268 MODERN TUNNELING 

sion and occasionally hurled for considerable distances down 
the tunnel. Where the plates are properly covered with waste 
rock from the previous round before blasting, however, such 
occurrences are so extremely rare as to be negligible, and this is 
ordinarily the remedy for such difhculty. But at the particular 
tunnel under discussion the trouble was somewhat different. 
It was being driven with a heading nearly square, and this was 
followed at a distance of eight to ten feet by a bench three to 
four feet high. The holes in the bench were drilled from the 
same set-up as those in the heading, and they "looked" down and 
away from the heading and hence toward and slightly under the 
position that would have been occupied by the steel sheets. It 
is not surprising that with this arrangement a great amount of 
difficulty should have been experienced in keeping the plates 
down during the short time they were tried. The objection in 
this instance should not have been taken to the steel sheets, but 
to the design of the tunnel itself, which was being driven consid- 
erably higher than it was wide, but would have served every 
purpose required of it equally well if the dimensions had been 
reversed. Such a change would not only have obviated the sheet 
trouble, but would also have made it easier to drive in other 
respects. Aside from this, the tunnel was not high enough to 
warrant the removal of the material in two operations, as was 
being done at the time it was visited. Since then, however, the 
bench was abandoned, all of the material being excavated at 
once, which made it possible for the mucking to be done without 
difficulty from steel plates. 

The third criticism is entirely a question of economy and can 
best be met by inquiring whether it is not better for the muckers 
to spend fifteen or twenty minutes while the drillers are loading 
the holes, and possibly as much more time during the mucking, 
in doing work that will save itself several times over. For it 
cannot be denied, and has been proved time and again, that a 
man can work to much better advantage and handle more rock 
during a given time if he shovels from a smooth surface. And this 
is only what is to be expected when one reahzes that in so doing 
he encounters but very Httle resistance other than friction in 



METHODS OF MUCKING 2(39 

pushing the shovel home, and is therefore able to secure a shov- 
elful with the minimum expenditure of energy and in the shortest 
time. But when shoveling from the pile, the shovel can rarely 
be pushed more than an inch or two without encountering 
a piece of rock too big to be shoved aside (although the effort 
is usually made to do so), and there must, therefore, be a distinct 
stop while the shovel, with any load upon it, is lifted clear of 
the obstruction, only, in all probabihty, to encounter another 
one almost immediately. It is not surprising, therefore, to find 
that the experience at a large majority of tunnels leads to the 
conclusion that steel plates for shoveling are among the chief 
economies. 



CHAPTER XIV 
TIMBERING 

MATERIALS 

When the rock through which a tunnel is driven does not 
possess sufficient strength and rigidity to carry the weight of 
the superincumbent mass, artificial supports for the roof, sides, 
and sometimes for the bottom are necessary to prevent the rock 
from falling, crumbling, or squeezing into the excavation. These 
supports may be timber, brick, stone, metal, or concrete. Because 
of its cheapness and availabihty in many mining districts, and 
the ease with which it can be cut to the required sizes and shapes 
and placed in position, the first of these is the one most generally 
employed; and even where masonry or concrete lining is called 
for in the specifications of the completed tunnel, timber is almost 
always used as a temporary support until the more permanent 
material can take its place. 

In most underground situations seasoned timber is prefer- 
able to green because it is better able to resist decay; and the 
bark should invariably be removed from round logs, as the 
space between it and the wood affords an excellent breeding-place 
for many forms of wood-destroying insects, while the bark itself 
collects moisture and thus encourages the growth of fungi which 
are the chief wood-destroying agents. Round timbers when 
properly peeled and seasoned are more durable than square 
timbers cut from a similar log of the same size and age, because 
the corners of the latter are especially liable to decay. In young 
and small timber, such as is generally used for mining work, 
the outer half of the log is usually sapwood containing starch, 
sugars, proteids, and other soluble organic compounds, the foods 
upon which decay-producing fungi thrive, and which are practi- 
cally wanting in the heart wood. In the process of squaring up, 
where, as is usually the case, the attempt is made to secure the 
largest possible square timber from a given log, the corners 

270 



TIMBERING 271 

consist largely of this easily infected sap-wood and are accordingly 
most liable to conditions bringing about quick rotting. It is 
not surprising, therefore, to find in moist underground workings 
where square timbers have been in place for three or four years 
that the corners of the timbers have decayed to such an extent 
that they can be pried off down to the heart wood with a miner's 
candlestick or any other sharp instrument. It is, of course, 
true that the outer portion of a round log also consists of sap- 
wood, but the exposed surface has not been injured or bruised 
by the saw. 

While round timbers deteriorate much more slowly than 
square, they are not so easily handled in the tunnel, and they are 
also harder to ahgn properly; it is also much more difficult to 
reinforce them by the ordinary false sets or pieces. Where 
timber must be transported long distances the greater weight 
of the round sticks (especially where the logs are truncated 
cones — or ''churn-shaped," as the miners say — instead of being 
nearly cyHndrical), the freight costs become prohibitive and 
square timbers must be used. Under these conditions the 
saving in transportation charges will often pay for some type of 
preservative treatment to be appKed to the timbers before being 
placed underground. 

The best method of checking the growth of fungi, and by so 
doing increasing the durabiHty of timber, is to poison the source of 
their food supply, and although there have been many processes 
invented for this purpose, most of those in use to-day depend 
upon the injection of either zinc chloride or creosote. The 
former cannot be used advantageously in wet situations, how- 
ever; for since it is soluble in water it would soon be leached 
out, leaving the timber just as susceptible to attack as before. 
But when creosote has been properly appHed it cannot be 
washed out, no matter how much water passes over the timber, 
and for this reason it is the preservative generally employed in 
mining and tunnel work. It is, however, somewhat more costly 
than the former, and since it is a hquid, the transportation 
charges are considerably higher, while the zinc chloride can be 
shipped in bulk. 



272 MODERN TUNNELING 

Creosote can be applied as a surface coating by painting 
with a brush or simple immersion in a tank, or the log can be 
more deeply impregnated with the preservative by one of the 
more complicated processes involving heat, pressure, or vacuum. 
Although painting is the least efhcient method, it has the ad- 
vantage of cheapness, and if carefully done will give fairly 
satisfactory results. While dipping or simple immersion results 
in but little if any greater penetration of the preservative, it 
insures a more certain filling and coating of the cracks, checks, 
and other imperfections of the log and thereby affords better 
immunity from decay. It is also in most cases cheaper than 
painting because it is more economical of labor, it being easier 
to run a number of sets of timber through a vat on some form 
of mechanical conveyer than to paint the same number by 
hand. For either method the timber must be fully dried arid 
seasoned beforehand, otherwise cracks in the wood due to the 
evaporation of the moisture will break the protective covering, 
which is only a thin one at best, and thus give the fungi access 
to the interior of the stick. It is perhaps unnecessary to add that 
these, as well as any of the other treatments, should not be given 
the timbers until after they have been cut to .form, so that the 
ends and the mortise openings may be coated as well as the sides. 

Where the extra cost of a more thorough impregnation is 
warranted, the ''Bethell" process is widely employed for timbers 
that are to be placed in wet situations. By this treatment the 
timber is for several hours given a bath of live steam at perhaps 
twenty pounds pressure, after which it is subjected to a vacuum 
for three or four hours more, when creosote, heated to a tem- 
perature of approximately i6o° F., is applied under pressure 
until the desired amount of the preservative is forced into the 
wood. ''Burnettizing" is a process practically identical with 
this, except that zinc chloride is used in place of creosote. There 
are also a number of methods less frequently employed which are 
designed to effect economy in the amount of chemical required, 
and which differ chiefly in the manner of its application. In 
one or two of them the interior of the timber is impregnated 
with the less expensive zinc chloride which is in turn protected 



TIMBERING 273 

from the action of water by treating the outer zone with creosote. 
A more complete discussion of processes than can well be in- 
cluded in this book may be found in Forest Service Bulletins 
78, ''Wood Preservation in the United States," and 107, ''The 
Preservation of Mine Timbers." 

For permanent tunnel linings, brick and stone were formerly 
the chief materials employed and most of the older tunnels both 
in this country and abroad are hned in this manner. Such Hnings 
are expensive, however, and require a higher class of labor to 
place them in position than does concrete, their modern sub- 
stitute, nor do they afford the same imperviousness. Although 
metal beams and posts are sometimes employed advantageously 
as roof supports in the main entries and gangways of coal mines, 
high cost prevents their use except for this or work of similar 
importance. The best modern material for permanent linings is 
undoubtedly concrete; and although its employment in this 
work has thus far been restricted chiefly to railroad, irrigation, 
or water-supply tunnels, its use in practically every important 
mining tunnel where a permanent lining is necessary must 
almost certainly follow. 

TYPES* 

The simplest forms of roof support are of course a post, or 
single timber supported by a "hitch" or recess in the side wall. 
Where the sides of the tunnel are not strong enough to afford a 
hitch, the ends of the cap are supported by posts; and if the 
floor will not bear the weight of the posts, a sill is placed for 
them to rest upon. Figure 65 illustrates such a four-piece set 
applied to as small a tunnel as it is usually advisable to excavate. 

* As tunnels and adits for the purpose covered by this book are rarely 
too large to be driven as a single heading, the many complicated and ingenious 
systems of timbering which are used in driving large railway tunnels, either 
with multiple headings or single heading and bench work, need not be 
considered here. For a discussion of these methods the reader is referred to 
the monumental work of Drinker ("Tunneling, Explosive Compounds, and 
Rock Drills," Drinker, Henry S., New York, Wiley & Sons); to Prelini (" Tun- 
neling," Prelini, Charles, New York, Van Nostrand); Stauffer ("Modern 
Tunnel Practice," Stauffer, David McNeely, New York, Engineering News), 
and the publications of the Civil and Mining Engineering Societies. 



274 



MODERN TUNNELING 



The timbers are 8 inches by 8 inches, and instead of partially 
beveling them to withstand side pressure the posts are held 
apart by a 2-inch by 8-inch plank spiked to the cap. Figure 66 




Fig. 65. Four- piece set of timbers for a small tunnel. 



u. ^^'^^^" 


J^^6"x6 


jj 


i'Q'- 


\\ 




Car 


w 


1 


^ 


\ \ 


.1 T 18" T 


\ \ 


M'^ 6"xl0" ^^ 



r 



1 



'6^8" 
Fig. 66. Four-piece set for a tunnel of a convenient size. 



illustrates a very common form of timbering designed for a 
tunnel of a convenient size for driving where a single track is 
all that is required. The timbers are 10 inches by 10 inches and 
the joint between the cap and the posts is beveled at the corners 



TIMBERING 



275 



SO that the timbers can easily resist horizontal or vertical pressure 
without splitting. If heavier ground is encountered than can be 
held with this set, the posts and cap can be made of 12-inch by 




Fig. 67. Arrangement of timbering providing a 
manway at one side of the tunnel 




Fig. 68. Timbering for a wet tunnel. 



1 2-inch timbers, with 8-inch by 12-inch sills, and 8-inch by 8-inch 
collar ''braces," as they are commonly called. 



276 



MODERN TUNNELING 



In single-track tunnels where there is considerable traffic, it 
is often advisable to have the opening wide enough to give room 
for a manway and the ventilating pipe on one side and the car 
tracks on the other, as shown in Figure 67. Or if the tunnel has 
to carry a considerable volume of water, the design shown in 




Fig. 69, Timbering for a tunnel producing a large volume of water. 



Figure 68 has been used in many instances and has given excel- 
lent satisfaction, notwithstanding the fact that both the opening 
and the timbers are unsymmetrical. The 6-inch by 6-inch sill, 
which also forms the rail tie, is not notched into the post on the 
right side, but is merely held in place by a 2-inch by lo-inch plank 
spiked to the face of the post, the upper end of the plank being 
recessed for a depth of 4 inches to receive the sill. Where 
even larger volumes of water have to be provided for, the arrange- 
ment illustrated in Figure 69 has given very good results at a 
number of places where it has been tried. The amount of water 
and the grade of the tunnel, of course, determine the proper 



TIMBERING 



277 



depth of the drain. The sill is supported by planks spiked to 
the posts, as in the preceding case. 

Where the roof pressure becomes too great to be carried by a 
h9rizontal cap, what is known as the ''arch set" is usually em- 
ployed. Figure 70 shows the design of such a set for a tunnel 




6"x6" m 




8"x^ 



Fig. 70. Arch set for a 
small tunnel. 



Fig. 71. Arch set with 
vertical posts. 



7 feet 6 inches high by 6 feet wide on the sills. The timbers are 

8 inches square and the collar braces 4 inches by 6 inches. In- 
stead of placing the braces on the outer edges of the timbers, as 
is done on square sets where they can be shpped in from the 
outside, the collar braces on arch sets should be mortised into 
the face of the timbers in a central position, bisected by the 
joint, as shown in the illustration. By this means the bevel 
pieces forming the arch, being much more difficult to hold in 
place while being blocked than are square sets, are prevented by 
the braces from slipping. If more room is required in the upper 
portion of the tunnel than is given in this design, vertical posts 
are often used (see Figure 71), a substitution which not only 
increases the width of the tunnel at the shoulders but calls for 
all timber cuts at an angle of 30°, making the sides and the top 
pieces of the arch interchangeable. Figure 72 illustrates the 
arch system of timbering as employed in medium heavy ground 
for a tunnel 8 feet in width by 7 feet 6 inches in height, which is 



278 



MODERN TUNNELING 



about the minimum size for a double- track tunnel. If the walls 
of a tunnel are sufhciently firm to stand without timbers and 
onty the roof requires support, the arrangement shown in Figure 
73 can often be used to advantage. This system makes a carp- 




FiG. 72. Arch set for a double-track tunnel. 




Fig. 73. Arch roof 
support and hitch. 



Fig. 74. Inverted arch set 
for swelling ground. 



fully constructed footing for the arch timbers necessary, but 
hitch-cutting with a modern hand pneumatic drill is compara- 
tively a cheap operation, the cost of which will be repaid many 



b 



TIMBERING 



279 



times by the saving in timbers and in the smaller amount of 
rock to be excavated. 

SweUing or creeping ground results from the exposure of cer- 
tain rocks to the air, whereby they undergo chemical change 
and increase in volume so that the excavation not only closes in 
from the sides and roof but swells up from the floor as well. 
Under such conditions it is sometimes necessary to design the 
timbers as shown in Figure 74, where the drain box and the 
track are protected by an inverted arch. Where 12-inch by 12- 
inch timbers in this form will not resist the squeeze at the usual 
distance of 4 feet between centers it- is customary to close 
them up until they have sufficient resistance to withstand the 
pressure. Occasionally, however, zones of rock are encountered 
that cannot be held even by this expedient, in which case the 
timbers can be kept from breaking by placing the sets about 
3 or 4 inches apart; then, whenever the pressure becomes too 




Fig. 75. Octagonal set of tunnel timbers. 

great, it can be reduced by removing with a long-bladed pick 
whatever decomposed rock is in Hne with the open spaces, 
4 or 5 inches back from the timbers. SwelHng ground is usually 
so soft that this can be done without much trouble, and it is 
neither a difficult nor an expensive matter to keep a wood- 
lined tunnel open until it can be Hned conveniently with concrete, 
which, by preventing access of air to the rock, will remove 



280 MODERN TUNNELING 

much of the difficulty. The octagonal set (see Figure 75) offers 
another means of holding such heavy ground, and it is often advis- 
able to follow it up with concrete in front of and between the 
timbers as shown on the left side of the illustration. To insure 
the safety of the tunnel after the timbers have decayed, the sets 
should not be spaced less than 12 inches apart, while 15 to 18 



Fig. 76. Timbering for loose ground. 

inches is still safer, since the wider opening gives room for a 
stronger rib of concrete between the timbers. The above is 
an exceedingly easy section to handle, and, where the flow of 
water is not too great for the drainage area underneath, nothing 
better could be adopted. All the pieces in this timber set are 
exact duplicates, and this is a great convenience not only in 
framing, but also in storage and erection. 

An entirely different problem from swelling ground, and one 
temporarily much more difficult to handle, is often encountered 
where adits or tunnels have to be driven through shear zones, 
caved ground, or loose crushed material which will not stand 
overhead without being supported as fast as it is opened. One 
of the oldest designs for driving through areas of this description 
is shown in Figure 76, where each alternate set carries a double 
cap. This arrangement is simple, easily operated, and very sat- 
isfactory where the material in the roof or sides does not bring 
too much pressure on the spiling.* The method possesses, 

* Where the lining of a tunnel can easily be placed in position it is usually 
known as lagging, but where it has to be sharpened to a chisel-shaped end 
and driven into position it is called spiling or forepoling. 



TIMBERING 



281 



however, two grave disadvantages: it requires two different sets 
of timbers, and the spihng used must be long enough to cover 
both sets. This latter difficulty, where the overhead material is 
heavy, sometimes proves serious, as it is often difficult to drive 
spihng across one space, to say nothing of two. 

Under such conditions, the tail-block system, illustrated in 
Figure 77, is generally employed. Since the timber sets are all 




Fig. 77. Tail-block system of timbering. 



the same size, it avoids one disadvantage of the preceding case, nor 
do the sets dift'er in any particular from those used with ordinary 
lagging. It off'ers, however, but httle improvement in the 
matter of driving the spiling in place. To be sure, the spiling 
does not have to cover two sets, but where the ground is heavy 
the great pressure brought upon the tail-block by a comparatively 
small amount of rock resting over the spihng as it is being 
driven forward creates an amount of friction which, added to the 
resistance in front of the spile, makes driving exceedingly difffcult 
even with the heaviest sledges that can be used. Even if the 
greatest care be taken, the back end of the spile is often broomed 
and spht by the heavy pounding required. This can be obviated 
in part by capping the back end of the spile with an iron shoe, and 
a heavy piston drill is sometimes employed to do the pounding. 
Where the ground over the tunnel is very much shattered and 
weak, making the continued hammering on the spiling dangerous, 
it is safer to force the spiling slowly forward with hght jack 
screws, and thus avoid the jarring effect of sledges. 



282 



MODERN TUNNELING 



When an opening has to be driven for any considerable 
distance through soft material requiring immediate support, 
the work can be expedited greatly by the use of what is known 
throughout the West as the swinging false-set, illustrated in 
Figure 78. Like many other inventions, this system was the 
child of necessity and was first used in the Cowenhoven tunnel, 
at Aspen, Colorado, where the overlying rock brought so much 
pressure on the spiles that it was almost impossible to drive 




Fig. 78. Swinging false-set for loose ground. 



them forward with an eighteen-pound sledge. With this 
method no tail-blocks are employed, nor need the spiling be 
driven across two sets of timbers as in Figure 76. The weight 
on the front end of the spiling is carried directly on the swinging 
false-set, and the spiHng can be driven into place with a quarter 
of the hammering necessary under the tail-block system. As 
will be seen by inspection of the longitudinal section, the posts of 
the swinging false-set rest and rotate on the sill of the permanent 
set and when first erected occupy the position shown by the 
dotted lines. They carry a circular steel cap h, which supports 
the front end of the spile a, so that the only pressure to be 
overcome in driving is that of the rock immediately above and 
in front of the spile, and it is consequently much easier to drive 
it forward than in the tail-block system, where a weight of 100 
pounds on the front of the spile would easily cause a pressure of 
five times that amount on its supports. As the spiling is driven 
forward the turn-buckle c is slowly unscrewed, allowing the 



I 



TIMBERING 283 

swinging false-set to fall forward and carry the point of the spiling 
in a nearly horizontal line. When all of the spiles have been 
driven home and the supporting block d is placed under them, 
the turn-buckle c is unscrewed still further, permitting the 
hanging rods to be unhooked from the eye-bolts and the false- 
set advanced to a new position, one set farther ahead. The 
system requires that the timbers for at least five or six sets from 
the face shall be bolted together in very much the same manner 
as hanging-bolts are used in placing shaft timbers; this, however, 
is a direct advantage rather than the reverse, for by bolting the 
timbers together and screwing them tight against the braces, 
they can be placed in position much more easily and quickly. 
Further, the timbers are held together so firmly that if hard 
ground is encountered in any part of the face, much heavier 
charges of explosives can be used than if they were held in place 
merely with blocks and wedges. The swinging false-set works 
equally well with square or arched sets, but where the latter are 
used the collar braces should be shifted from their normal 
position on the center hne of the timbers, as shown in Figures 70, 
71, 72, and 74, to the outer end of the joints to make room for 
the greatest possible width of spiKng; by this means the angle 
gap can be reduced to a minimum and the length of the 
''lacing," correspondingly reduced. 

In driving a heading where the character of the rock neces- 
sitates timbering close to the face, care must be taken thoroughly 
to brace and block the front sets before firing. Where the roof 
''breaks high" and there is any possibiHty of large masses 
dropping out of it, the space between the lagging and roof must 
be completely filled either with waste or blocking, otherwise a 
large piece of rock may drop from the roof and pass completely 
through the lagging, and thus endanger the Hves of the men 
below. Timbering close to the face always diminishes the 
rate of progress by compelling the use of shallower holes and 
lighter charges. An excellent plan to permit of heavier rounds 
under these conditions is to keep the last six or eight sets of 
timbers firm and tight up against their collar braces by the use 
of tie bolts. These should be provided with center hooks to 



284 MODERN TUNNELING 

permit of their ready removal, on the same plan as the hanging 
bolts which have so long been successfully used in shaft sinking. 
Only six or eight sets of bolts are required, those from the rear 
being moved forward and used in the face. This system of 
tying the sets together has been found to be equally advantageous 
in horizontal and in vertical driving. 

The tunnel shield, such as is generally employed with or 
without compressed air for piercing subaqueous river-bed 
deposits, affords another solution of the problem of driv'ng 
through soft ground. While in the matter of speed, safety, and 
economy the modern shield leaves little to be desired, it has one 
great drawback — the initial cost of the installation — which prac- 
tically bars it from use for the narrow zones or small areas of 
running ground usually encountered by the class of tunnels we 
are considering in this book. 

The system of timbering employed at the north end of the 
Elizabeth Lake tunnel of the Los Angeles Aqueduct is of especial 
interest because of the ingenious and extremely effective means 
employed to drive through a comparatively hard rock which, 
however, was so shattered and broken that it could not be trusted 
to stand even temporarily without support; in addition, the 
speed and efficiency with which the timbering was placed in 
position were notable, enabling as they did the north end of the 
tunnel to progress practically as fast as the south, although in 
the latter but very little timbering was required. The following 
description is taken, with some condensation and re-arrangement, 
from an article by R. L. Herrick, in Mines and Minerals for 
October, 1910. 

The main tunnel, which was approximately 12 by 12 feet, 
was preceded by a short pilot heading having dimensions of 
approximately 8 feet by 8 feet, in which the roof was supported 
by '^ false" timbering. Assuming for convenience the time of 
inspection to have been at the end of a shift with the drills re- 
moved from the breast preparatory to blasting the round, the 
position of the timbers would have been somewhat similar to 
that shown in Figure 79 (a), which represents a short timbered 
section of the full-sized tunnel and the horizontal timbers used 



TIMBERING 



285 



temporarily in supporting the roof of the pilot heading. The 
posts of the permanent sets were 8-inch by 8-inch square timbers, 
8 feet 6 inches in length; and in the figure they are spaced longi- 
tudinally at eight-foot intervals, although in practice they were 
often set irregularly, depending upon the weight of the roof. 




SECTION A-B SECTION C-D SECTION E-F 

Fig. 79. System of timbering at Elizabeth Lake tunnel. 



The width between the posts was 10 feet 2 inches in the clear, 
while the tunnel was broken as nearly as possible to a width of 
12 feet. The collar braces were ordinarily 2-inch by 6-inch planks 
whose ends were supported either by wedges or timber-ends 
spiked to the set. The false posts in the heading were later used 



286 MODERN TUNNELING 

as permanent posts for the full-sized tunnel, and as one end of 
them was beveled to carry pieces of the permanent arch, these 
beveled ends were placed next the floor in the heading, while 
their squared ends supported the temporary caps, which likewise 
consisted of timbers already cut to form and which were later 
used as permanent posts. In this way there was no handling of 
heavy timbers not intended for permanent use. Just before 
blasting, the false timbers were carefully braced and wedged to 
the roof as tightly as possible, as shown in Figure 79 (b). 

As soon as possible after the blasting the timber-men went 
back to the heading to shore up the new roof temporarily from 
the top of the rock pile. For this purpose, two horizontal 
timbers, supported from the broken rock close to the side walls 
and having transverse timbers and blocking resting upon them 
as shown in Figure (c), were placed by the timber crew, an 
operation which interfered but little with the work of the muckers 
shoveling back from the, face to allow the placing of the drills. 
The debris was next removed down to solid bottom to permit 
the setting of false posts which, when capped, then carried the 
weight of the roof. 

Timbering the tunnel during the enlargement to full size 
was not a difiicult operation. Starting at the last permanent 
set and proceeding toward the face, new permanent posts (shown 
in a, Figure 79) were placed in position as fast as the section was 
widened by picking down the side walls. Transverse spreader 
timbers, shown in section CD, Figure 79, were then placed be- 
tween these posts with their bottoms 14 inches below the joint 
and resting on timber ends spiked to the posts. Across these 
spreaders wxre laid two tiers of two-inch plank, forming a floor 
4 inches thick. This floor was some 2 or 3 inches below the 
bottoms of the caps resting on the false posts, so that it was 
easily laid while the false sets continued to hold the roof. Work- 
ing from the end of this floor, the wedges and blocking trans- 
mitting the roof weight to the false set were next carefully 
knocked out and the shattered roof picked down on the floor, 
from which it was later dropped into cars. By placing the 
permanent posts a foot or so in advance of the false posts as in 



TIMBERING 287 

a, Figure 79, the arch timbers of the permanent sets. could be 
put in position as soon as the roof was sufficiently removed. 
Lagging and wedging quickly followed, so that the roof was 
supported by the permanent sets shortly after the removal of 
the false blocking. 

Although lining a mining tunnel with concrete is not, strictly 
speaking, a type of timbering, both have the same function — 
that of supporting the roof and walls. In this work the concrete 
is usually placed in the openings between the timbers and for 
a few inches in front of them, which, where the sets are not spaced 
too closely together, is generally sufficient, even though later 
decay of the wood results in a corresponding weak spot in the 
lining. This defect can be avoided, howTver, by the use of posts 
and caps made of reinforced concrete in place of wood, a practice 
which has been recently introduced and which is finding great 
favor wherever its added expense is warranted. The concrete 
posts and caps are made outside of the tunnel in a mold which 
gives them the identical form of the w^ooden pieces they displace ; 
and by proper reinforcement they can be made equal, if not 
superior, to timbers in strength, a strength which is practically 
permanent. 

In water-supply tunnels a concrete lining performs the 
additional function of obviating eddies and friction against the 
otherwise irregular walls, and for this reason such tunnels are 
generally lined throughout, irrespective of the needs of the roof 
for support. On the Los Angeles Aqueduct the tunnel lining 
was generally at least 8 inches in thickness where the tunnel was 
not timbered, although an occasional rock projecting into the 
concrete was not removed unless it came within 4 inches of the 
inside finished surface of the lining. In timbered ground, con- 
crete was placed between the timbers and for a minimum dis- 
tance of 4 inches in front of them. The inverted siphons of the 
Catskill Aqueduct were lined with concrete which was ordinarily 
2 feet thick, but solid rock was permitted to project without 
removal to within 10 inches of the interior surface. Owing to 
the great hydrostatic head, sometimes as high as 700 feet, to 
which these linings w^ere to be subjected, every piece of timber 



288 



MODERN TUNNELING 



was removed before the concrete was put in place, and where 
it was necessary to support the roof during the time the concrete 
was setting, steel roof supports were designed and placed for this 
purpose. 

At the Snake Creek tunnel (where a zone of swelling ground 
was encountered which resisted all efforts to hold it in the ordi- 
nary way, the strongest timbers that could be obtained being 



CEriangtilaT mesli e-creen, weight 106 pounds per 100 square feet 



3)<Jtal thickness of 
concrete 13 " 



52-poun(l 
crown ra" 



SECTION A A 

-Thickness of concrete 
outside of J. ill IJ^-" 



S'six-Tiole splice,- 

^'bolts. Fishplate 

cross section 2% 

square inches each. 




Regulation railroad 
fouEshole fishplate 



Fig. 8o. Reinforced concrete lining at Snake Creek tunnel. 



crushed and broken in less than a month's time) a concrete 
lining reinforced with steel rails was installed. T'he accompany- 
ing illustration of this lining is practically self-explanatory, but 
a complete description of it may be found in the Engineering 
Record for May 25, 191 2. Where large volumes of water have 
to be carried through ground extremely difficult to hold, this 
design seems excellent, although its cost would be prohibitive 
for anything except important tunnels draining large areas of 
well-developed ground. 



CHAPTER XV 
SAFETY 

Data collected by the Bureau of Mines show that an average 
of nearly four men for each i ,000 employed in and about the metal 
iTiines of the United States were killed during the year 191 1, as 
compared with t^.S per 1,000 in coal mining during the same 
period. Although complete figures for accidents in tunnel 
driving cannot be obtained, a study of such data as it was pos- 
sible to collect indicates that the number of deaths per year per 
thousand men employed has been somewhat greater than the 
above figures, the result obtained by averaging data extending 
over periods of from one to ten years for sixteen representative 
tunnels being 4.7 deaths per year per 1,000 men employed. 
In addition to the men kihed outright, nearly four times as 
many more have been seriously injured, or perhaps maimed for 
life, and almost thirteen times as many slightly injured by acci- 
dents in tunnel work. By far the largest portion of these deaths 
and injuries were caused by falling ore or rock from the roof or 
walls of the tunnels, but the careless use of explosives, haulage, 
electricity, and other causes have each claimed their quota 
of casualties. 

Are these accidents preventable? Not entirely, because there 
are some elements of danger impossible to ehminate and inherent 
in the work of driving tunnels; such, for example, as the danger 
from some unforeseen falls of roof, from the derailment of tunnel 
cars, or the certain risk when handling even the safest explosives 
by the most approved methods. But it is equally true that much 
of the present mortality and injury is the result of ignorance or 
gross carelessness, and can be avoided. When, for instance, a 
man sees fit to thaw frozen dynamite in a frying pan or by a 
candle flame, there is nothing accidental about the explosion 
which ensues, except, indeed, the fact that a man so ignorant or 

289 



290 MODERN TUNNELING 

reckless should have been entrusted with so dangerous a sub- 
stance! Nor is the responsibility for accidents entirely on the 
part of the miner. The manager and his representatives are in 
many cases either ignorant of the precautions which should be 
taken for the safety of the men under them, or most negligent in 
seeing that they are properly and consistently carried out. The 
following paragraphs are written, therefore, in the hope that, by 
bringing these matters once more squarely to the attention of 
the men interested, much of the needless death and suffering 
may be prevented. 

CAUSES OF ACCIDENTS 

Falls oe Rooes 

There are many causes which combine to make falls of rock 
from the roof by far the greatest source of danger in tunnel work, 
but perhaps the chief of these is the common practice of greatly 
overloading the holes with explosives. Extremely heavy charges 
shatter and crack rock which would ordinarily stand without 
any danger of falling, and render it extremely dangerous to the 
men working underneath. Of course, it is essential to efficient 
work in tunnel driving that the blast should completely ''break 
bottom" without any necessity for a second loading and firing; 
still every foreman and superintendent should see to it that the 
very smallest amount of dynamite that will do the required work 
is employed in the holes near the roof. Economy of explosive 
demands this, all other considerations aside; but the dangers , 
also, of the heavier charges should be thoroughly appreciated by 
the superintendent and, when such charges seem imperative, 
extra vigilance should be exercised and extra precautions taken 
along other lines for the safety of the men. 

Another prolific source of accident is the fact that men will 
sometimes return to the tunnel face, after shooting a round, 
without thoroughly testing the new roof just exposed by the 
blast. It should be the duty of every man employed in the 
tunnel to examine the roof under which he must work, and 
especially in that part of the tunnel newly exposed after shoot- 



SAFETY 291 

ing; the foreman, upon reaching the heading after the blast, 
should at once detail one or two men (or as many as prove 
necessary) to clean down thoroughly all the loose pieces of over- 
head rock. Fortunately, this is done regularly at all well- 
organized tunnels, and it is a practice that cannot be too highly 
recommended for universal use. 

It must be admitted that there are times when even ex- 
perienced men believe the roof to be sound, when suddenly 
and without warning a large block crashes into the tunnel. 
This, if anything, will be claimed as a purely accidental occurrence, 
yet even the danger from such a rock (which may have been 
perfectly sohd when first exposed, but had become loosened 
by the concussion of subsequent blasting) is, in many cases, 
overlooked because of the lack of illumination in which all 
tunnel work must be done, and might have been discovered in 
time if there had been a systematic and regular examination of 
the entire roof of the tunnel. As some one has pointedly ob- 
served, "The fall of a slab of rock weighing anything less than 
one ton should at once be charged to carelessness." 

It should be said in this connection that the ''sound" of 
the roof is not a proper criterion of its safety, since there are 
on record numerous cases in which the sound of the roof was 
satisfactory and showed apparently solid rock even to very ex- 
perienced men, but in which a big block or boulder was actually 
loose. The better method of testing the roof — one used by many 
large mining companies and recommended by the Bureau 
of Mines — is to strike it with a pick or a heavy stick, at the 
same time touching the doubtful piece with the free hand. If 
any vibration is felt, the rock is unsafe and should be taken down 
or supported at once. If the roof is too high to reach with the 
hand, a stick should be held against the doubtful piece while it 
is being struck, and if it is loose the vibration can be felt through 
the stick. 

Prompt and adequate timbering is extremely important. 
But timbering is a laborious process, and it either takes the men 
of the tunnel crew from their regular work or it requires extra 
men. Even in the latter event the extra men add to the confu- 



292 MODERN TUNNELING 

sion in the heading; and since their work is done simultaneously 
with the other work of the tunnel, it seriously hinders either the 
drillers or the shovelers, or both. Hence it has become recog- 
nized among tunnel men that in most cases timbering seriously 
impedes the progress of driving, and therefore, although it may 
be well understood that the roof is dangerous, there is almost 
always a tendency on the part of those responsible to delay 
timbering as long as possible. Perhaps the American willingness 
to ''take a chance" — a trait particularly noticeable in our 
Western States — may be a contributing cause; but the fact 
remains that the work of timbering is too often delayed until a 
so-called ''accident" brings the necessity forcibly and unavoid- 
ably to the front. It is impossible to urge too strongly that all 
necessary timbering be done promptly, that it cannot be done too 
soon, and that any delay seriously jeopardizes the lives and limbs 
of the men who have to work under a roof improperly supported. 

It is true that in many tunnels the weight of the roof or 
pressure against the walls has been too great even for the strongest 
and heaviest timbering, and while this cannot always be pre- 
vented, it may often be alleviated by means discussed in the 
chapter on timbering. But the important thing to consider 
in these cases, from the viewpoint of safety, is the fact that 
actual failure of the timbers and caving of supported ground 
rarely come without warning. Either the timbers will at least 
be bent quite appreciably before they break, or, as is usually 
the case, they will crack and splinter and so give unmistakable 
warning to the miner that the time is approaching when they 
will collapse. The only way in which accidents can occur in 
such cases is by carelessness or negligence in heeding the danger 
signal. It may be said in this connection that, other things 
being equal, timber which has a fiber that will split, crack, or 
splinter out, rather than that which has a fiber that will break 
off short under a transverse strain, is on this account more 
desirable for such work. 

Falls of rock are also caused by cars becoming derailed and 
knocking out the supporting timbers under a heavy or loose 
portion of the roof, allowing this material to fall and kill or 



SAFETY 293 

injure any men who happen to be underneath. Such accidents 
are in many cases unavoidable because of the difficulty in 
preventing derailments. Owing to the lack of illumination, it is 
usually impossible to see whether the track ahead is clear, and 
it is therefore necessary to run more or less bhndly and assume 
that nothing has fallen upon the track since the last trip; besides, 
the mere work of keeping the road-bed of a tunnel track in such 
shape that its unevenness would no longer cause the cars to 
jump off would be enormous. The only way, therefore, to 
lessen these accidents (which are fortunately not so numerous 
as those from other causes) is to keep the track in as good a 
condition as possible and to use all reasonable watchfulness 
and caution in tramming. 

Use of Explosives 

Next in importance as a cause of injury in tunnel work is 
the careless, reckless, improper, or ignorant use (or rather 
misuse) of explosives. Such accidents are of various kinds, 
the most frequent being those arising from handling, storing, 
and thawing dynamite, from premature blasts, from misfires, 
or from suffocation by gases from explosives. 

PRECAUTIONS 

While the follow^ing list, which has been compiled from a 
number of sources, does not pretend to be complete, it is given 
here in the hope that it may once more repeat some of the pre- 
cautions to be observed in the handling and use, not of dyna- 
mite alone, but of the accessories of blasting as well. 

Handling: 

Don't forget the nature of explosives, but remember that 
with proper care they can be handled with comparative safety. 

Don't smoke while handling explosives, and don't handle 
explosives near an open light. 

Don't shoot into explosives with a rifle or pistol, either in 
or out of a magazine. 



294 MODERN TUNNELING 

Don't attempt to manufacture any kind of an explosive 
except under the supervision and direction of a trustworthy 
person who is skilled in the art. Many serious accidents, 
which have destroyed lives or inflicted injury on persons and 
property, have been caused by such attempts. 

Don't carry blasting caps or electric detonators in the clothing. 

Don't tap or otherwise investigate a blasting cap or electric 
detonator. 

Don't attempt to take blasting caps from the box by inserting 
a wire, nail, or other sharp instrument. 

Don't try to withdraw the wires from an electric detonator. 

Storing: 

Don't leave explosives in a wet or damp place. They should 
be kept in a suitable, dry place, under lock and key, and where 
children or irresponsible persons cannot get at them. 

Don't store dynamite boxes on end, as this increases the 
danger of nitroglycerine leakage from the cartridges. 

Don't store or handle explosives near a residence. 

Don't open packages of explosives in a magazine. 

Don't open dynamite boxes with a nail-puller or powder 
cans with a pick-axe. 

Don't store or transport detonators and explosives together. 

Don't store fuse in a hot place, as this will dry it out so that 
uncoiling will break it. 

Don't keep electric detonators, blasting machines, or blasting 
caps in a damp place. 

Don't allow priming (the placing of a blasting cap or electric 
detonator in dynamite) to be done in a thawing-house or magazine. 

Thawing: 

Don't use frozen or chilled explosives. Most dynamite 
freezes at a temperature between 45° F. and 50° F. 

Don't thaw dynamite on heated stoves, rocks, sand, bricks, 
or metal, or in an oven, and don't thaw dynamite in front of, 
near, or over a steam boiler or fire of any kind. 

Don't take dynamite into or near a blacksmith shop or near 
a forge. 



I 



SAFETY 295 

Don't put dynamite on shelves or anything else directly over 
steam or hot-water pipes, or other heated metal surface. 

Don't cut or break a dynamite cartridge while it is frozen, 
and don't rub a cartridge of dynamite in the hands to complete 
thawing. 

Don't heat a thawing-house with pipes containing steam 
under pressure. 

Don't place a "hot-water thawer" over a fire, and never put 
dynamite directly into hot water or allow it to come in contact 
with steam. 

Loading: 

Don't allow thawed dynamite to remain exposed to low 
temperature before using it. If it freezes before it is used, it 
must be thawed again. 

Don't fasten a blasting cap to the fuse with the teeth or 
by flattening it with a knife; use a cap crimper. The ordinary 
cap contains enough fulminate of mercury to blow a man's 
head or hand to pieces. 

Don't "lace" fuse through dynamite cartridges. This 
practice is frequently responsible for the burning of the charge. 

Don't explode a charge to chamber a hole and then immedi- 
ately reload it, as the bore-hole will be hot and the second charge 
may explode prematurely. 

Don't force a primer into a bore-hole. 

Don't do tamping with iron or steel bars or tools. Use only 
a wooden tamping stick with no metal parts. 

Don't handle fuse carelessly in cold weather, for when it is 
cold it is stiff and breaks easily. 

Don't cut the fuse short to save time. It is dangerous 
economy. 

Don't worry along with old broken leading mre or connecting 
wire. A new supply will not cost much and will pay for itself 
many times over. 

Firing: 

Don't explode a charge before every one is well beyond the 



296 MODERN TUNNELING 

danger line and protected from flying debris. Protect the supply 
of explosives also from this source of accident. 

Don't hurry in seeking an explanation for the failure of a 
charge to explode. 

Don't drill, bore, or pick out a charge which has failed to 
explode. Drill and charge another bore-hole at least two feet 
from the missed one. 

Premature Explosions 

It is very often difficult to determine just what are the 
causes of any particular premature explosion, because in such 
cases the persons responsible for the explosion rarely survive 
to tell the tale,, and even eye-witnesses are scarce ; but careless- 
ness in handling the dynamite in the heading is no doubt the 
most potent factor. In many cases the so-called accident does 
not result from the first instance of carelessness or of reckless- 
ness, but is the disastrous climax of a series of practices that 
have become habitual, so that persons knowing the common 
disregard for dynamite on the part of the men who handled it 
and were killed are able to draw very accurate conclusions 
as to the probable cause of the "accident." As an example of 
this, we cite the case of two men who were accustomed to throw 
sticks of dynamite to each other along the tunnel, over dis- 
tances of fifteen or twenty feet, especially if visitors with ''nerves" 
were present. But even at other times, perhaps because of 
long familiarity with dynamite and hence a contempt or dis- 
regard of its great dangerousness, the sticks were thrown to 
each other rather than have the trouble to walk the few inter- 
vening feet. The practice was finally stopped, however, as far 
as these two personally were concerned, by a disastrous ex- 
plosion in which they were blown almost to atoms, and which 
(judging from the subsequent appearance of the tunnel) was 
probably caused by the detonation of a stick falling near the 
full supply for the entire round. 

Another cause of premature explosions is the practice of 
carrying dynamite to the face of the tunnel in a box or sack 



SAFETY 297 

and dropping it quite roughly to the ground at the end of the 
journey. This contempt is also bred, no doubt, by famiharity. 
It is true that oftentimes gelatine dynamite is not so sensitive 
to direct shocks as one might imagine, and that many times 
it will stand very rough usage without detonation; but in other 
cases, and there are very many of them on record, serious ex- 
plosions have ensued when the care in handling might almost 
be called extreme. It is therefore neither safe nor advisable 
to rely in any degree whatsoever upon the '^inertness" of 
dynamite, but at all times great care should be exercised in 
handling it, if not out of regard for one's own security, then 
for the sake of the lives and safety of fellow workmen. Nor 
is it possible to condemn too strongly the practice of carrying 
the denotators or the primers (sticks of dynamite containing a 
detonator and a fuse) in the same bundle with the rest of the 
supply of explosive for the round. They should always be 
brought in separately and should under no circumstances be 
placed in the same box, or even near together, after reaching 
the heading. Many serious accidents have resulted through 
disregard of this rule. 

A certain amount of risk must always attend the loading of 
a bore-hole with dynamite, especially during the insertion of 
the primer, but much of the danger which often needlessly ac- 
companies this w^ork can be minimized or avoided by care 
and caution in its performance. It is, of course, essential to 
efficiency that there shall be no air spaces in the charge of ex- 
plosive when it is finally ready for detonation, and in order to 
insure this the dynamite must be rammed. down so that it fills 
all the unequal spaces in the bore-hole; but the packing should 
always be done by pressure rather than impact, for some miners 
use a tamping bar as if it were a javelin. But even when pressing 
down the charge, great care must be taken that too much force 
is not employed, especially when a cartridge seems to stick in a 
hole; for should it become suddenly loosened, the miner might 
not be able to recover himself in time to prevent its being rammed 
hard against the bottom, with diastrous results. Anything 
more than light pressure should never be given the primer^ and 



298 MODERN TUNNELING 

under no circumstances should it or the succeeding cartridge 
be struck a blow with the rod. 

Irregularity in the rate at which fuse burns is also a cause 
of premature explosions. Different makes and brands of fuse 
burn at greatly varying rates and a miner accustomed to a 
slow-burning fuse will perhaps not realize the necessity of cutting 
the faster fuse longer, so that he may have time enough to reach 
a place of safety before the detonation takes place. But there 
are several causes which may produce variations in the burning 
rate even of the same brand of fuse. For example, experiments 
conducted by the Bureau of Mines * show that mere confinement 
in a closed vessel is sufficient to cause a fuse to burn three or 
four times faster than its normal rate. It is true that under ordi- 
nary conditions of mining variations of this magnitude are not 
apt to be reached, but irregularities of 20 per cent, or even 30 
per cent, are quite possible, and in long bore-holes in which a 
quantity of tamping is used, and especially if it be of a type 
impervious to the escape of the gases (such as closely packed 
wet clay), the variation may be much greater. Therefore, 
where such tamping is used, the rate of burning may be increased 
to a dangerous extent, unless due allowance be made for this 
extra speed. But even more important is the effect produced by 
mechanical injury, which is more apt to be a common occurrence. 
Mere bending of fuse (if it is in proper condition for use), such 
as might result from coiling it near the collar of the hole to 
prevent its being struck by flying rock from other blasts, or 
even placing it with some force within the hole, has but little 
if any effect upon the fuse; but abrasion, blows, or too great 
pressure produce serious variations in its rate of burning and 
in some cases may even cause it to burn almost instantaneously. 
It is therefore essential that none but fuse in good condition 
ever be brought into the heading, and that care be taken while 
it is there to see that it is not injured by rocks or tools falling 
upon it, and that it is not abraded or otherwise injured with the 
tamping bar while the hole is being loaded. . 

Mention must be made of the apparently obvious danger of 

* Technical Paper 6. 



SAFETY 299 

reloading a bore-hole before it has had time to cool off sufficiently 
from a previous blast. In tunnel work this appHes particularly 
to the ''guns," as they are called — the ends of holes that have 
not broken to the bottom with the first explosion — and accidents, 
either through carelessness in not examining the holes or a desire 
for haste overcoming better judgment, have been caused by 
too early reloading of these guns after the first blast. 

Misfires 

Many deaths and injuries are caused by the subsequent 
detonation of a charge of dynamite which failed to explode at 
the proper time, though misfires do not mean accidents unless 
the unexploded dynamite is detonated unexpectedly in some 
way. Sometimes this is done by drilKng into it during prepar- 
ations for the next round, or by striking it on the muck pile 
where it has been thrown by the blast from a neighboring hole, 
or perhaps by the sudden explosion of a delayed shot from a fuse 
that has long been smoldering. 

A large portion of these misfires can be traced directly to 
some injury to the fuse. The insertion of the primer into the 
hole, fuse-end first, often causes a crack in the fuse at the sharp 
bend thus produced (and the danger of cracking it in this way 
is especially great when the fuse is cold or the hole is full of 
cold water), or sudden and rough uncoiKng of the fuse in cold 
weather will usually cause it to break. It is therefore obvious 
that cold fuse should not be bent, twisted, or roughly handled. 
It is claimed by some persons that misfires are caused through 
the fuse being cut off ahead of the fire in it by the explosion of a 
neighboring hole, so that consequently the charge of dynamite 
fails to explode. There is some question whether this really 
happens or not; but if it does, it is a pretty strong argument that 
the hole in question was probably misplaced, for if it was properly 
located, only in rare instances, if ever, would enough of the hole 
be shot away to cut oft" the fuse ahead of the fire. It is also 
claimed, and with somewhat more reason, that the fuse is apt 
to be torn out by flying rocks from the explosion of other holes, 
but this can be largely obviated if the fuse is properly coiled, as 



300 MODERN TUNNELING 

it should be, close to the mouth of the hole before it is 
''spit." 

The failure of a fuse properly to ignite a detonator is often 
caused by improper storage. When the asphalt water-proofing 
composition used in some fuses gets too hot, it becomes viscid 
and agglomerates the powder grains in the core of the fuse, and 
thus delays, and in some cases actually prevents, the fuse 
from burning. Experiments conducted by the Bureau of 
Mines * indicate that prolonged exposure at a temperature of 
60° Centigrade is sufficient to cause a marked retardation in 
the rate of burning. It follows, therefore, that fuse should not 
be stored near boilers, steam pipes, or other sources of heat, 
where the temperature is apt to be high. The effect of cold is 
likewise deleterious, for it renders the asphalt composition 
brittle and liable to crack, and these cracks either decrease the 
rate of burning by permitting the gas from the powder core to 
escape more readily than usual, or, if they are large enough, they 
may stop the travel of the fire entirely. The fuse should be 
carefully protected from moisture during storage; for, with 
water-proof fuse of the type almost universally employed in 
tunneling, if the dampness once gets into the powder train it is 
very difficult to get it out. As the fuse burns, this moisture is 
driven ahead of the fire in the form of steam, and even if it 
does not thus accumulate in sufficient quantity to quench the 
fire in the fuse, enough of it may be driven into the detonator 
to prevent its ignition and thus cause a misfire. 

Misfires originate in many cases from improperly prepared 
primers. Before inserting the fuse into the detonator, an inch 
or two should be cut off and thrown away, for gunpowder 
(which forms the core of the fuse) being somewhat hygroscopic, 
the end of the fuse may have gathered sufficient moisture to 
quench the burning powder or prevent the ignition of the cap; 
this cut should be made with a sharp cutting tool squarely 
across the fuse, for if cut diagonally the point may curl over 
the end of the fuse when inserted in the detonator and thus 
prevent the spit of the powder train from reaching the gun- 

* Technical Paper 6. 



SAFETY 301 

cotton (or the mercury fulminate) in the cap, causing a misfire. 
Care should also be taken that the powder grains in the end 
of the fuse do not leak out after the fuse is cut, for this would 
tend to weaken the force of the spit into the detonator and might 
prevent its ignition. The free end of the cap should be carefully 
crimped around the fuse with a proper crimping tool, so that it 
will be tight enough to hold the detonator and the fuse together 
and keep out moisture, but the crimping should not be tight 
enough to cut off the powder train in the fuse. This is par- 
ticularly liable to happen when a narrow crimping tool is em- 
ployed, which presses a very narrow groove in the detonator 
and the underlying fuse. There are tools on the market which 
have a crimping face of at least a quarter of an inch, and the 
extra purchase price of several of these tools would be no more 
than the cost of the explosive wasted by a single misfire, to say 
nothing at all about the possible loss of fife that might arise 
from it. It is of course obvious that the teeth or a knife should 
never be used for crimping; for, as we have said, there is enough 
explosive in an ordinary detonator to blow a man's head or 
hand to pieces. After crimping, the detonator should be buried 
in the end of the stick of dynamite wdth its axis parallel to that 
of the stick, and the top of the detonator should be flush with the 
top of the dynamite; for if the cap is buried deeper, the explosive 
is Hable to become ignited from the side-spitting of the fuse 
before it is properly exploded by the detonator, which not 
only destroys the efficiency of the explosive, but causes a larger 
amount of gases, especially those most dangerous to the men 
who must breathe them. It is also important to use a detonator 
of sufficient strength. Although 3 X caps were considered 
strong enough for straight nitroglycerine dynamite, the less 
sensitive gelatine dynamite requires a much stronger detonator 
to explode it properly. For this reason nothing weaker than 
5 X caps should ever be used with gelatine dynamite and the 
universal experience is that better results have been obtained 
where a change has been made to an even stronger detonator. 
These insure the complete detonation of the explosive and 
thus produce only a minimum amount of dangerous gases. 



302 MODERN TUNNELING 

It is very difficult to count the explosions during blasting 
and be sure that the charges have all been detonated, so that 
it is not always possible to determine whether or not there has 
been a misfire. For this reason the face, or as much of it as is 
not covered by the debris resulting from the blast, should at 
once be inspected for evidences of missed holes, and it should 
be carefully watched during the removal of the muck. If a 
missed hole is discovered, under no circumstances should an 
attempt be made to pick out the material. If no tamping has 
been used, as is usually the case in tunneling, a stick of dynamite 
containing a detonator should be inserted in the hole and exploded 
at once; if tamping has been employed, another hole should be 
drilled and blasted at least two feet from the missed one. In 
picking down the muck pile the pick should be handled as if it 
were a hoe and not like a sledge hammer; i.e., the material should 
be pulled or scraped down and never struck violently with the 
point of the pick. In this way, should there happen to be a piece 
of unexploded dynamite in the debris, there is much less danger 
of an explosion resulting from it, with a corresponding injury 
and loss of life. The importance of this precaution cannot 
be too strongly emphasized. Should a piece of dynamite be 
discovered in the muck, it should be removed carefully and 
handed to the foreman, who should at once take it to a safe 
place, and the most extreme care should be used if a piece of 
fuse accompanies it or is discovered near it, for this would 
indicate that an unexploded detonator may possibly still be 
inside of the stick of dynamite, the danger of which is obvious. 
Under no circumstances should a new hole be started in the 
remnants of a former hole that has ever held dynamite; for 
although the inference is always, of course, that the dynamite 
has been detonated, still there remains a chance that this might 
not have occurred — a chance not so slight as might ordinarily 
be supposed, to judge from the number of accidents traceable 
to this source. And even if a rod is used to test the hole, it 
might encounter a small rock and, by thus seeming to show the 
bottom of the hole, fail to reveal the dynamite beneath. 



SAFETY 303 

Suffocation by Gases from Explosives 

Suffocation from the gases produced by explosives is a common 
source of injury in tunnel work. Cases of this kind are famihar 
to most miners; it is usually called ''powder headache" in its 
mild form and produces little more than temporary incon- 
venience, but in severe cases it has been known to produce death 
within a very short time. In the chapter on blasting it has 
already been explained that the harmful gases resulting from 
the complete detonation of dynamite under normal conditions 
are usually carbon dioxide and carbon monoxide; that although 
the former will not support respiration, and when present in 
sufficient quantities may cause unconsciousness and even death, 
it has no very injurious effects when sufficiently diluted ; that the 
latter is exceedingly dangerous and even small amounts of it 
may prove fatal if breathed for a sufficient length of time. It 
is this gas which probably causes the familiar symptoms after 
a dose of "powder smoke." By a reference to the table on page 
238 it will be seen that gelatine dynamite, the type almost uni- 
versally used in tunnel work, under proper conditions generates 
a comparatively small amount of the more dangerous gas. 
Experiments conducted by the Bureau of Mines indicate that 
even this can be obviated by a slight modification in the chemical 
composition of the gelatine dynamite. But even if such a 
dynamite is not completely detonated (either through the use of 
too weak a detonator or for any other cause), and especially 
when it burns rather than explodes, a much greater amount of 
monoxide is formed and, in addition, a number of other harmful 
gases are developed, among which may be mentioned the danger- 
ous peroxide of nitrogen. It is therefore essential that deton- 
ators of sufficient strength be employed to explode the dynamite 
completely, and that every precaution be taken to prevent the 
dynamite from taking fire through the side-spitting of the fuse 
or in any other manner. 

The deadliness of the gases resulting from explosives im- 
properly detonated may be illustrated by describing one oc- 
currence which is known to have cost nine fives. A study of 



304 MODERN TUNNELING 

the attendant circumstances, as described in a communication 
to the writers, indicates that the explosive, or a large portion 
of it at least, must have burned rather than detonated. Gelatine 
dynamite was employed and the charge was even smaller than 
previous blasts of which the men had inhaled the fumes with- 
out serious effects, but in this case the fumes are described by 
the men as having been brownish-yellow rather than the usual 
grayish or bluish-white. After igniting the blast the men retired 
about 500 feet to wait for the smoke to clear, and while they 
were waiting the smoke drifted slowly over them, and then, 
owing to some change in the current, drifted slowly back again. 
The men soon felt the usual symptoms of carbon monoxide 
poisoning — slight choking, nausea, profuse perspiration, and 
headache — but they all revived upon reaching the open air 
about an hour and a half after the blast was fired. Within a 
short time, however (and in one case before the man could walk 
to the bunk-house), the men began to cough up bloody mucus 
and exhibit other symptoms of nitrogen-peroxide poisoning, 
and in less than three days nine of the thirteen men who had 
been in the tunnel and exposed to the fumes had died. The 
four who escaped were either not exposed to the gas for the full 
time, or else found some other source of air supply which served 
partly to dilute the gases; but some of these men, as well as those 
who went in with the motor to bring the men out, were ill for 
days and even months after the catastrophe. A full discussion 
of the customary symptoms that accompany poisoning from 
nitrogen peroxide and carbon monoxide, and their comparison 
with the symptoms exhibited by the men, will be found in the 
April, 191 1, number of Colorado Medicine, and it is the opinion 
of physicians who have studied this case that many swift deaths 
among miners, formerly diagnosed as pneumonia, may really 
have been caused by the inhalation of gases from burning 
dynamite. 



SAFETY 305 

Suffocation by Gases and Other Sources 

Although the chief source of any carbon monoxide that is 
liable to be encountered in tunnel work is usually to be found 
in the dynamite employed, there have been cases in which this 
dangerous gas was generated by the combustion of oil and 
grease in the air-receiver and transmitted to the heading by the 
compressed-air pipe. The causes of such combustion have been 
fully discussed in the chapter on air compressors, so that it 
need merely be mentioned here that the ignition of accumulated 
oil and grease is generally due to faulty valves in the compressor. 
These permit leakage back into the cylinder of the warm com- 
pressed air, which, upon being recompressed, becomes still hotter, 
so that after a time the temperature of the air in the receiver 
may be built up far beyond the ignition point of the lubricant 
employed. If an explosion does not then ensue, the oil on the 
sides and bottom of the receiver will burn and produce carbon 
dioxide or carbon monoxide, as the case may be, either of which 
jeopardizes the safety of the miner in the heading. It is, there- 
fore, necessary to inspect the valves of the compressor regu- 
larly; what is more, dependence should never be placed on 
the compressed-air line for tunnel ventilation. 

There are a number of tunnels in which natural deposits of 
gas have been encountered, the two kinds most frequently found 
being carbon dioxide and hydrocarbon gases. The former is, of 
course, chiefly dangerous because of the possibility of the men 
being overcome by suffocation, but this can largely be obviated 
by sufficient ventilation, although sometimes at a considerable 
additional expense. As an instance in point, one of the tunnels 
on the Los Angeles Aqueduct might be mentioned, in which 
currents of carbon dioxide were encountered in a series of crevices 
across a zone about 150 feet wide. In order to make it possible 
for the men to work in the tunnel, this zone and 300 feet on 
each side of it were tightly sealed with concrete; in addition, it 
was found necessary to leave an annular space back of the con- 
crete in the center of the gas zone, to which a blower was con- 
nected that constantly exhausted the gas during the driving of 



306 MODERN TUNNELING 

the tunnel, while an additional blower forced in fresh air to the 
men. When either of these machines ceased operating, it was 
necessary for the men to get out of the tunnel as fast as possible, 
but as long as they were kept running the air was sufficiently 
pure. 

The chief danger from hydrocarbon gases Hes in their explo- 
sibility, but they are so commonly met with in coal mining that 
precautions to be taken in their presence are fairly well known. 
A rather unique method of dealing with this problem, however, 
— a method which is well worth a description — was employed in 
one of the tunnels examined by the writers. 

The gas was encountered in a zone approximately 2,300 feet 
in extent, through about 500 feet of which oil could be distilled 
from the rocks, although it did not flow of itself. The gas was 
highly explosive and had an odor of kerosene or gasoHne rather 
than that of crude petroleum. The largest quantities of it came 
into the tunnel immediately after blasting, from the rock broken 
by each new round, and the maximum accumulation was approx- 
imately 30,000 cubic feet. There appeared to have been no 
particular seepages in the gaseous zone, but rather an unknown 
quantity ahead of the work that had always to be reckoned with. 
Since the gas was highly explosive, extra precautions had to be 
taken for the safety of the men at work. The mere restriction 
of permitting no open-flame lamps and requiring safety lamps 
in the tunnel was not considered sufficient here, although that 
is the usual practice in coal mines where similar gases are encoun- 
tered, because the very nature of the rock was such as to cause 
sparks from a pick or from the starting of a drill hole, and such 
sparks were thought to be sufficient to ignite the gas and produce 
an explosion. The expedient adopted was to explode the accu- 
mulation after each blast and to burn any new gas as fast as it 
appeared in the tunnel during the remainder of the work. 

For this purpose the tunnel was wired from the portal to the 
heading with a 5 50- volt circuit, into which were introduced at 
intervals of about 200 feet, throughout the entire gas-bearing 
section, a number of arcing devices. Any ordinary street arc 
lamp could have been adapted for this work, provided that the 



SAFETY 307 

carbons were not exposed for more than two inches; otherwise 
the concussion from ordinary blasting, as well as from the gas 
explosions, would have broken them. The use of one soft and 
one hard carbon was found to give the best results. This system 
was operated as follows: 

Immediately after blasting, a fire boss and his helper took 
charge of the tunnel. Waiting thirty minutes after the blast 
was fired, they turned a current of electricity through the arc 
line by means of a switch at the portal. Since the arcs were 
purposely placed in series, in order to make certain that if any 
one of them burned they must all necessarily do likewise, an 
ammeter at the control switch showed whether or not they 
had lighted. If such was the case, an explosion, which sometimes 
would be a severe one, generally ensued. But whether this 
happened or not, the switch was always opened for fifteen minutes 
and then closed a second time as an added precaution, although 
a second explosion never resulted from thTs operation. With 
the line dead once more, the two men carrying safety lamps 
then proceeded to a protected station approximately half-way 
to the heading, where they again sent a current through the arcs. 
A few explosions resulted from this practice, but they were un- 
usual rather than customary. After having made this test, the 
fire boss and his helper then proceeded to the heading, testing 
the entire tunnel for gas by means of the safety lamps they 
carried. They would ordinarily find an accumulation of gas in 
the heading, extending back a distance of 125 to 150 feet, because 
the nearest arc could not be placed much nearer to the heading 
than the greater of these distances on account of the danger 
of the carbons being broken by the concussion from the blasting. 
The fire boss would then take an arc which was kept 150 feet 
from the face and which was attached to the circuit by an 
armored cable, and place it over the muck pile, when the two 
men returned again to the midway station and once more 
closed the circuit and ignited the remaining gas. Then, and 
then only, and with all the arcs burning, they returned to the 
heading and placed torches as near the roof as possible at inter- 
vals of about 150 feet throughout the gaseous section. These 



308 MODERN TUNNELING 

torches were lighted from the arcs, and the men were not per- 
mitted to light them in any other way, or indeed to carry any 
other means of lighting them into the tunnel, thus insuring 
that there should be open fire in the heading before the torches 
were Kghted. By this time all the seepages that were strong 
enough to support a steady flame would have been lighted and 
would be burning, while the gas that came from pockets that 
could not sustain a flame would be ignited by the torches before 
it could accumulate in any quantity. The fire crew then returned 
to the mid-station, where they extinguished a red light and 
lighted a white one, indicating that the tunnel was safe for the 
incoming crew, for no one but these two men was allowed in 
the tunnel beyond this point unless the red light was out and a 
particular white one was burning.* The fire crew were allowed 
four hours for this work, although it did not ordinarily take them 
so long. 

The working crew, upon reaching the heading, ordinarily 
found the muck pile too hot to handle, if, indeed, it was not 
actually in flames, for it burned usually for from one-half to 
two hours after each blast, while once, at least, it burned for four- 
teen hours. After it had been cooled sufficiently by streams of 
both air and water, the machines were set up and the round of 
holes drilled in the regular manner. Any gas that developed 
during the drilHng of a hole was lighted as soon as the hole was 
completed, and if sufficiently strong to support a flame, it would 
burn until the end of the shift, and at one time as many as six 
out of eight holes on the top round were burning like blow-torches, 
givitig flames six to eighteen inches in length. When the round 
was finished, the holes had to be cooled before loading. This 
was accomplished by turning water and air lines through ordi- 
nary blow-pipes, both into the holes and over the face of the tun- 
nel. The flames were, of course, extinguished by this process, 
and as soon as the gas had accumulated in the tunnel sufficiently 
to become apparent in a safety lamp placed near the roof, about 
thirty feet from the heading, it was ignited by a torch, and the 

* To obviate danger through any accidental extinguishing of the red Hght 
without the knowledge of the fire crew, and before the tunnel was safe. 



S.^ETY 309 

resulting flames were at once put out again by air and water. 
This process was continued until the holes were cool, when 
they were at once loaded as rapidly as possible, and fired, the 
fuses, in doing so, being always lighted from near the bottom of 
the tunnel. 

Although the fact that there were no accidents in driving 
through the gas-bearing zone after the installation of the '' safety 
arcs" shows that this system was efficacious in this particular 
instance, it is not one that can be recommended unqualifiedly 
for general use. In the opinion of engineers who have made a 
special study of the question of safety in mining, the use of 
anything but safety lamps, or their equivalent, in mines or 
tunnels where explosive gases are known to exist, is never with- 
out risk, while the practice of burning the gases as fast as they 
make their appearance is in itself extremely hazardous. Indeed, 
the fact that no disastrous explosion occurred under this system 
seemed to them remarkable. Aside from this, it is obvious 
that long delays were necessary before the men could start to 
work, and even after they had reached the heading, the heat 
must have greatly decreased their possible efiiciency. A less 
dangerous method of handling a similar situation, and one that 
would probably prove more economical in the end if everything 
were taken into consideration, would be the installation of a 
ventilating system large enough to dilute to harmlessness several 
times the amount of gases ordinarily encountered, combined with 
the absolute prohibition of any but safety lamps in the tunnel, 
and the firing of all blasts by electricity. 

Haulage 

A large proportion of the injuries attributed to tramming 
is caused by the practice of riding on the cars, and especially 
upon the loaded ones. When riding upon the top of a full trip, 
a man is always in danger of a serious injury at every low place 
in the roof, and if he is riding between the cars (or any place 
but the rear end) he is Hable to be jarred from his foothold and 
dragged under the cars, while he has httle chance of escape in 
case of derailment. A certain risk of derailment is unavoidable 



310 MODERN TUNNELING 

in tunnel work, partly because of the insufficient illumination 
under which tramming is generally carried on, and partly 
because of the difficulty, almost the impossibility, of keeping 
the road-bed in good condition or the track clear of small obstruc- 
tions. 'Even when riding upon empty cars there is serious risk 
whenever the miner sits upon the ends or sides and allows his 
feet to hang over; the safest way is to sit inside of the car and 
to crouch low enough to avoid being struck by any jutting place 
in the roof. The driver, or ''mule skinner," is often compelled 
to ride upon a loaded trip and sometimes at the front end of 
the train in order to be near the animal he is driving, but the extra 
hazard of this position should be fully realized and extra pre- 
cautions taken. The practice observed on the part of some 
drivers, of riding with one foot on the bumper and the other 
on the chain by which the mule is attached to the first car of the 
trip, the danger of which is obvious, cannot be too strongly con- 
demned, and it should be made cause for the instant dismissal 
of any driver caught doing it. It ought not to be necessary to 
mention the danger of attempting to jump on or off a moving 
trip of cars, because the chances in such a case of a man missing 
his footing and being caught or dragged under the cars, or of 
breaking an ankle or leg in the uncertain light, should be so 
clearly seen that no one ought to consider the risk worth taking; 
but the number of injuries arising from this cause shows only 
too well that this precaution is habitually disregarded. 

Great care is necessary during the operation of placing a 
derailed car back upon the track. It is very easy for a miner 
to strain or otherwise injure himself if he attempts to do this 
without getting some one to assist him. Also in handHng a 
derailed car that is full of rock there is danger of block or crow- 
bar slipping and allowing the car to drop suddenly on the miner's 
foot or hand, if indeed it does not topple over completely and 
crush him against the side of the tunnel. 

Failure to allow sufficient room to a passing trip of cars is 
also a frequent source of injury. Before going into a strange 
tunnel the miner (or any one else for that matter), if he is not 
accompanied by some one familiar with the tunnel, should always 



, 



SAFETY 311 

ascertain upon which side of the track there is the most room, 
and in meeting a passing trip should always give an animal 
pulling it all the space possible, to avoid being tramped on or 
kicked by the horse or mule or being caught between the cars 
and the walls of the tunnel. It is also advisable to hide any light 
when meeting a horse or mule, for there are some animals that 
are afraid, especially of the high-powered acetylene lamps that 
are coming to be used almost entirely in tunnel work; they will 
balk when coming toward one and cause a serious mix-up, 
since the cars behind cannot always be stopped at once. Respect- 
ful attention in a tunnel, as on the surface, should always be 
given the heels of animals whether moving or at rest, and it is 
best to speak to them when approaching from behind, for many 
serious injuries have been caused by passing too close to nervous 
animals without warning. The driver also, when turning a horse 
or mule around in a heading, should watch carefully to see that 
he is not stepped on; inane as this advice sounds, many really 
serious accidents have resulted from just this simple cause. 

Electricity 

An examination of reports of electrical accidents in tunnel 
work shows that in the majority of cases the shocks were caused 
by the trolley wire. This is not surprising when one considers 
the many factors which unite to make electricity especially 
dangerous underground. In the first place, the earth is ahnost 
always used to complete the return circuit, and therefore, if the 
miner inadvertently touches any portion of electrical apparatus 
that is charged with current, and if he is not well insulated 
from the ground, he will certainly get a shock the intensity of 
which depends upon the voltage or pressure of the electric current 
and the incompleteness of his insulation from the earth. It 
is to be expected that the trolley wire should be the chief source 
of electrical shocks, for it carries a current sometimes as high as 
600 volts without any insulating or protecting covering what- 
soever and generally without a guard or shield of any sort, 
while it is usually placed less than a man's height from the 
floor and has a rail beneath it to form a return circuit even 



312 MODERN TUNNELING 

better than the earth. Then, too, tunnels are generally damp 
or wet, so that a man is rarely well insulated from the ground; 
the light at best is poor and one cannot always see the wire as he 
approaches it, while the space is so restricted that a man in 
walking in and out must keep his head close to the wire when, 
at the same time, the most of his attention must needs be given 
to the question of footing. Then, too, when cHmbing into 
or riding in cars, which in tunnel work are almost always of 
metal and furnish excellent electrical connection with the rails, 
one's head must pass close to the live wire. The carrying of 
metal tools, such as crow-bars or drill steel (although picks and 
shovels are equally hazardous if the wooden handles are wet), 
is also the cause of many shocks through their accidental contact 
with the trolley, and this is especially liable to happen if such 
tools are carried on the shoulder. It is therefore important, 
when walking in a tunnel where a trolley wire is installed, con- 
stantly to bear its existence in mind and take every precaution 
to avoid contact with it by hand, wet clothing, or tools. 

In addition to the trolley wire, there are in tunnel work 
other sources from which electrical shocks may be received. 
Wherever the heading is illuminated by electricity, the Kghts 
are usually grouped in a cluster and connected to the main 
circuit by means of a flexible cable, so that they can be easily 
removed to prevent breakage during blasting. The wires of 
the cable are, of course, insulated in such cases, but owing to 
the rough usage they receive, it very often happens that the 
insulation is damaged or scraped off, leaving the bare wire 
exposed. Even if the injury is not severe, it is often sufficient 
to permit a considerable leakage of current from which a person 
handling the cable may receive a severe shock. Such wires are 
the more dangerous because, supposing them to be protected, 
one is more apt to handle them carelessly. The men who 
remove these wires preparatory to blasting, and replace them 
afterward or otherwise adjust them, should examine them 
closely and not touch any place where the insulation has become 
damaged. Shocks are also caused by motors, transformers, 
or other pieces of electrical equipment which are supposed to be 



SAFETY 313 

safe, but which may have become charged with current, or in 
the adjusting or repairing of switches and other similar devices, 
parts of which are known to be alive, but which are touched 
accidentally in the course of the work. In handhng apparatus 
of this sort, a workman should carefully insulate or otherwise 
protect himself from the current and should try to handle the 
apparatus in such a manner that any involuntary muscular 
reaction from a shock will throw him clear of its live parts 
rather than bring him in closer contact with them. Although 
electric locomotives are usually in such perfect contact with the 
rails that a person touching any accidentally charged part of the 
frame will rarely receive a shock, there are times (as, for ex- 
ample, when there is a considerable amount of dirt or sand on 
the rails) when the locomotive is almost completely insulated 
from them; in such a case any one coming in contact with a Hve 
portion of the frame or of the draw-bar, or even with one of 
the cars coupled to the locomotive, may receive a severe shock 
which is apt to be all the more serious because it is unexpected. 
For this reason the touching of such equipment should be 
avoided when not actually necessary. 

Mention should be made here of the immediate steps to be 
taken in case a man has received a severe electric shock and is 
perhaps lying unconscious and apparently dead from its effects; 
for it is often possible by prompt treatment to revive and restore 
a man in this condition when otherwise he might fail to recover 
consciousness. The best methods suggested for such cases may 
be found in Miners' Circular 5, pubHshed by the Bureau of 
Mines, a copy of which may be obtained free upon application 
to the Director, Bureau of Mines, Washington, D. C. 

Fire 

The chief danger to the men in a tunnel from fire is the 
possibility of the buildings at the surface becoming ignited. 
These structures are, of course, subject to the same causes of 
fire as ordinary buildings, such as the careless handling of matches 
or lights, spontaneous combustion of oily waste wherever it is 
allowed to accumulate, or the short-circuiting of electrical wires, 



314 MODERN TUNNELING 

not to mention the risk of forest fires in heavily timbered regions. 
At a large majority of tunnels now being driven, the blacksmith 
shop, the store room, the boiler house, or other buildings, are 
situated much closer than the 200 feet which should separate 
them from the tunnel portal, and in many districts, especially 
where the winter snowfall is heavy, they are directly connected 
with the tunnel by snow-sheds usually constructed of wood. At 
such tunnels, also, other means of exit than the portal are seldom 
provided, so that in case of fire in these buildings men are penned 
up in the tunnel and, in the customary absence of a fire door, 
they are in serious danger of suffocation from the gases and 
smoke produced by the conflagration. It is, therefore, essential, 
and in some States it is fortunately required by law, that in all 
tunnels where combustible structures must be erected nearer 
to the portal than 200 feet, there should be a separate exit at 
least 200 feet away, and a fireproof door should be provided in 
the tunnel that can be closed from a distance. At the same 
time a sufficient water supply should always be maintained to 
put out an incipient fire, and hydrants with a coiled i>^-inch 
hose and a nozzle should be placed not less than 40 feet and 
not more than 100 feet from each building or group of buildings. 
Although most tunnels are themselves practically fireproof 
(except where timbered) , and hence underground fires in tunnel 
work are not common, it is, nevertheless, important even here 
to guard against the dangers of fire. Whenever underground 
fires do occur in tunnels, they usually start in some small way, 
either from candles or lamps being placed too near the posts or 
caps of a timber set, or from throwing a match or the coals 
from a pipe into a pile of rubbish, hay, or other combustible 
material which may in turn ignite the timbering. Although 
such fires can usually be extinguished at once and before any 
great damage or injury has resulted, if their presence is dis- 
covered soon enough and if means are at hand for that purpose, 
it is much better to prevent the ignition by obviating causes. 
Therefore, combustible rubbish should not be allowed to accumu- 
late in the tunnel and any supply of hay for the use of mules or 
horses underground should be carefully confined in a bin pro- 



SAFETY 315 

vided for that purpose, while open lights or smoking should not 
be permitted in their neighborhood. Candles or torches should 
never be left burning near timbers, while the practice of wedging 
a lighted candle between two nails driven into a post should be 
cause for the instant dismissal of the guilty persons. 

Water 

Water under pressure is another source of danger in tunnel 
work, and men are hurt in jumping back to avoid the rocks and 
other debris often carried with it, or are perhaps buried under 
an accompanying rush of mud and sand. A good example of 
this may be found in the records of a foreign railway tunnel, 
where a cleft filled with water, sand, and gravel was encountered 
and the ensuing sudden and violent inburst of these materials 
filled up more than a mile of the tunnel in a very few minutes, 
burying twenty-five workmen and their tools beyond all hope 
of recovery. A somewhat similar occurrence in one of our 
American tunnels, although fortunately with less fatal results, 
was likewise due to water. The tunnel caved in at a point about 
4,000 feet from the heading, but the men working there were 
warned in time to escape, although they had barely reached 
safety before the tunnel became entirely closed. When this 
happened, the mass of rock, composed chiefly of soft clay and 
running shale impervious to water, cut oft' the main flow in the 
tunnel, which was approximately 2,700 gallons per minute. As 
soon as the portion of the tunnel between the cave and the 
heading became filled with water, the full pressure of the head 
in the mountain over the tunnel was exerted against the dam, 
forcing it down the tunnel until the pressure was reheved. The 
additional length of the debris then offered greater resistance 
and remained stationary until the pressure had again accumu- 
lated enough to move it, and this process was repeated until 
440 feet of tunnel had been filled. Several attempts were made 
at first to reheve the pressure by inserting a section of venti- 
lating pipe at the top of the dam; but after several men had 
narrowly escaped burial by the rush of mud as the dam moved 
forward, this scheme was abandoned and the tunnel was sealed 



316 MODERN TUNNELING 

up by a concrete bulkhead, the men being protected by a tempor- 
ary bulkhead of wood during the construction of the permanent 
one. 

In driving through Hmestone and dolomite it is not unusual 
for a tunnel heading to tap immense caves filled with water, 
mud, and sand. In such cases the volume of the fluid mass 
flowing into the tunnel is determined by the size of the opening, 
while its velocity is proportionate to the head. Under a pressure 
of 300 or 400 feet the cutting action of the rock particles and sand 
carried by the water soon enlarges even a drill-hole to a size 
that permits the filling up of the heading in an incredibly short 
course of time. When a round of shots breaks into a cave of this 
kind, the heading and perhaps the completed tunnel for a distance 
of hundreds and sometimes even thousands of feet back from the 
face may be filled so fast that the escape of the workmen would 
be impossible if they were in the face. Fortunately, however, 
at the time of greatest danger, viz., shot firing, the men are 
always out of the heading. 

When an underground cave or reservoir filled with water, 
mud, sand, and loose rock is tapped in a tunnel heading one of 
two things* occurs : generally the cave or reservoir empties itself 
completely into the tunnel and, after the flow is over, the solid 
matter which the flood leaves behind can easily be shoveled up 
and hauled out; but it sometimes happens that the volume of 
solids is so great that the tunnel is completely choked up before 
the reservoir is emptied. In these cases, when the flow of water 
ceases, the men are usually set to work cleaning up the material 
with which the tunnel has been filled, but when this cleaning-up 
process advances sufficiently to weaken the dam which is holding 
back the flood, a new outburst occurs and, because the passage- 
ways have already been opened, the second outbreak is often 
more violent and dangerous than the first. If this operation 
were repeated often enough, the cave or reservoir would of 
course be drained and the heading be regained, but in many 
instances the operation of attempting to regain the heading has 
been found so dangerous that it has been abandoned and a 
curved tunnel put in to pass around the danger point. 



SAFETY 317 

In the Cowenhoven tunnel, when the heading was in dolomite, 
caves of this kind, filled with water and dolomite sand, were fre- 
quently encountered, and it was no uncommon thing to have the 
tunnel completely filled for hundreds of feet back from the 
face after a round of shots. As soon as the water from the 
cave which had been tapped drained off, the mud and sand 
were easily loaded up and work in the face was resumed. On 
one occasion an immense cave of this kind was tapped by a 
drill-hole in a long cross-cut which was being driven from 
the tunnel to the Delia S. Mine, which, under the pressure 
and cutting action already described, enlarged so rapidly 
that the men fled from the face and, a few seconds after, the 
opening enlarged to a size which permitted the filling of the 
tunnel with such rapidity that the tunnel cars were hurled 
back and flattened against the posts. Several unsuccessful 
attempts were made to regain this face, which finally had to be 
bulkheaded and the tunnel run around it, as at the Loetschberg 
tunnel. 

In the 1,200-foot level of the Free Silver mine, which was 
likewise run through dolomite, numerous caves were also en- 
countered, but fortunately, while they must have extended to 
great heights, their horizontal cross-section was very much less 
than that of the caves 1,200 feet above. When these reservoirs 
were tapped with a drill-hole the water would spout out wdth 
such velocity that it was impossible to stay in the face, and in 
a short time the opening would be worn to a size which some- 
times increased the amount of water to be handled by the pumps 
to 3,000 and even 4,000 gallons per minute. At first the noise 
from the inrushing volume of water was exceedingly terrifying 
to the men, but "familiarity breeds contempt," and in a short 
time whenever a cave of this kind was tapped the men simply 
joined hands to assist each other in maintaining their footing 
and waded back with the torrent the same as they would do 
in crossing an extremely rapid stream. Many narrow escapes 
occurred, but, owing to the precautions taken by the manage- 
ment and workmen, no serious accidents occurred during any 
of these inrushes. 



318 MODERN TUNNELING 

Intoxication 

Although few accidents in tunnel work are traced directly 
to intoxication, the extent to which it contributes to many 
mishaps that are ascribed to other causes is perhaps too little 
appreciated. The fact that a man who has put an enemy 
into his mouth to steal away his brains is much more Hkely 
to be careless or negligent of his own safety and the Hves of the 
men around him is so well established as to need no emphasis. 
Even a slight degree of intoxication, that might be allowable 
if the work had to be done on the surface, is dangerous under- 
ground, where it is very apt to be greatly aggravated either by 
the lack of fresh air or by the heat, either of which is common 
in tunnel headings. Therefore it is essential that a man in such 
a condition should not be permitted underground and, if dis- 
covered there, should be immediately sent out of the tunnel 
by the foreman, while repeated offenses should result automatic- 
ally in dismissal. 

PREVENTION OF ACCIDENTS 

In discussing the prevention of accidents in tunnel work 
little is to be gained by saying that the manager or the foreman 
or the miner is solely to blame for their occurrence. The greater 
responsibility lying, as ever, with those who have the broader 
vision, the manager or the superintendent is in duty bound to 
see that the place where the men are to work shall be made as 
safe as possible and to insist that they, themselves, exercise the 
greatest care and caution in conducting their work. Then, again, 
accidents are costly, not only of life and limb, but usually from 
a financial viewpoint; for in many cases they either seriously 
hinder the work or cause it to be shut down altogether for 
months at a time, as, for instance, after a fire, or flood, or cave-in 
— catastrophes which in many cases could have been prevented, 
if even but ordinary precautions had been taken beforehand. 
So, both from the humanitarian and from the economic point 
of view, safety should come first, and the business of making the 



SAFETY 319 

tunnel safe for the men to work in should be considered more 
important than the driving of extra footage per month. Upon 
the foreman falls the responsibihty of carrying out the man- 
ager's orders, of seeing that the men are instructed in the 
proper precautions to be taken, and that these are constantly and 
consistently exercised, and, if necessary, of discharging either 
temporarily or permanently any man who wilfully or habit- 
ually disregards them. As for the miner, whose business is shown 
by statistics to be a hazardous one at best, it is only through 
the most extreme care on the part of each man, not only for his 
own welfare but for the safety of his co-workers, that he can 
hope to escape from the dangers that surround him. Each one 
has his share, therefore, of the responsibihty, and it is only by 
co-operation between all parties concerned that any progress 
can be made toward the prevention and reduction of the 
fataHties and the injuries now encountered in tunnel driving. 
Since it is impossible to reiterate too often the methods of 
obviating accidents, the following paragraphs are written 
directly for the parties most concerned, in the hope of 
bringing home to them once again some of the more important 
preventive measures. 

Precautions for the Manager or Superintendent 

Insist that necessary timbering be done at once and always 
keep an adequate supply of lumber at hand for this purpose, so 
that no delay may ensue from the lack of it. See that the min- 
imum amount of explosive is used (in order to prevent unneces- 
sary shattering of roof and walls) and inaugurate a systematic 
and regular examination of the roof to insure the removal of all 
loose pieces at once. Have all bent or breaking timber promptly 
replaced by new posts or caps. 

Pro\dde suitable magazines and thaw-houses for explosives.* 

Do not permit any disregard of the proper precautions in 

handhng, storing, or using explosives, such as are listed on 

* Specifications for such buildings recommended by the Bureau of Mines 
are to be found in Technical Paper i8, which may be had free on application 
to the Director, Bureau of Mines, Washington, D. C. 



820 MODERN TUNNELING 

pages 293-96, and see that each man is provided with a copy 
of these or similar precautions.* Do not permit the transporta- 
tion of detonators or primers to the heading in the same bundle 
with the remaining supply of explosive for the blast. Have 
careful tests of the burning rate of the fuse made periodically, 
especially whenever a different brand of fuse is purchased, and 
warn the men of any discovered irregularity. Destroy any 
damaged fuse at once. Do not store fuse near any source of 
heat. Prohibit the reloading of a bore-hole before it has had 
time to cool from a previous blast. Give the men proper tools 
and have them instructed in the correct way to prepare a primer 
and see that these instructions are obeyed. Do not purchase 
caps weaker than 5 X for use with gelatine dynamite. See that 
the proper precautions are taken whenever a missed hole or 
evidences of one are discovered. 

Institute a regular and frequent inspection of the valves on 
the air compressor and insist that any defective valve be promptly 
and properly repaired, even at the cost of a possible shut-down, 
that there may be no explosion of gas or burning of grease in 
the receiver or pipe-line to produce harmful gases and jeopardize 
the safety of the men at the heading. Do not delay the installa- 
tion of adequate auxiliary ventilating equipment when natural 
deposits of harmful gases are encountered in the tunnel, and 
this is particularly important when such gases are of an explosive 
nature. In the latter instance, none but safety lamps or their 
equivalent should be permitted underground. 

Prohibit the men's riding on loaded trips and, whenever 
possible, provide for their use special cars either propelled by 
hand or drawn by a motor. Do not permit them to jump on or 
off moving cars, nor the drivers to "ride the chain." Tell all 
new men the proper side of the tunnel to take when meeting a 
trip, and caution them to shield any bright light when so doing. 

If there is a trolley wire or other electrical apparatus in the 
tunnel, caution the men against its danger, and do not allow 

* A Miners' Circular containing these precautions may be obtained free 
from the Director, Bureau of Mines, Washington, D. C, by forwarding the 
names and addresses of the men for whom it is desired. 



SAFETY 321 

them to carry tools on their shoulders when passing in or out. 
See that the cables or wires leading to any temporary or movable 
cluster of lights in the heading are kept in good repair. Instruct 
the men, and especially the foremen, in the proper methods of 
resuscitation in case of electrical shock. 

Prohibit the accumulation of combustible rubbish anywhere 
in the vicinity of buildings or timbering and see that the supply 
of hay is properly confined to prevent danger from fire. Do not 
construct any wooden buildings nearer than 200 feet from the 
mouth of the tunnel, unless such are absolutely necessary, in 
which case provide a separate exit from the tunnel at least 200 
feet away, with a fire door so arranged that it may be closed 
from a distance. In either event, provide an adequate water 
supply, with hydrants and hoses, at suitable distances from the 
several buildings. 

Exercise great precaution when driving tow^ard a place where 
a flow of water is Hkely to be encountered that might carry 
with it a rush of mud, sand, gravel, or other debris, and take 
immediate steps for the safety of the men as soon as such a flow 
is struck. 

Prohibit the drinking of intoxicating Hquors on property 
controlled by the tunnel company, institute a system of inspec- 
tion to prevent any intoxicated man from working in the tunnel, 
and discharge habitual transgressors of this rule. 

Precautions for the Foreman 

Insist that the least amount of dynamite required for the 
work shall be used in loading the top holes. Do not go yourself 
or permit the men to return to the face after blasting, without 
examining the new roof, and upon arriving at the heading detail 
immediately as many men as may be required to clean the roof 
before any other work is attempted under it. Never fail when 
passing in or out of the tunnel to inspect the roof, testing any 
doubtful piece for possible vibration. See that any loose piece 
of rock is either pulled down at once or properly supported, and 
never take any chances by postponing the work of timbering, no 
matter how pressing other matters may be, because a few 



322 MODERN TUNNELING 

minutes' delay in timbering may cost several lives. Have any 
timbers showing the effects of too great pressure properly 
relieved as soon as they begin to fail. When timbering is neces- 
sary close to the face, see that the front sets are thoroughly 
braced and blocked before firing. When the roof ''breaks 
high" fill the space between the lagging and the roof with broken 
rock or blocking to prevent a large rock from crashing through 
the lagging upon the men beneath. 

See that the men read the precautions to be taken in handling 
explosives, or have a copy read to them. Do not permit any 
instance of careless or reckless handling of explosives to go 
unchallenged and do not fail to discharge men for the first grave 
offense of this character. Never permit a man to handle dyna- 
mite recklessly, either for the purpose of scaring some one or 
for any other reason. See that the detonators and primers are 
transported to the heading in separate boxes from the rest of 
the supply and that they are not placed side by side after arriv- 
ing. Insist that proper care be used in loading holes and that 
the tamping be done by pressure rather than by impact. Never 
allow anything but wooden bars to be used for this purpose. 
Do not permit a bore-hole to be loaded before it has had sufficient 
time to cool completely from the previous blast. 

Warn the men of any change in the rate of burning of fuse. 
See that they do not mutilate it by rough handling or that it is 
not cracked or broken by placing the primer in the hole fuse-end 
first, or by uncoihng the fuse roughly in cold weather. Do 
not use fuse that has been stored or kept near a boiler, steam - 
pipe, or other source of heat, or that has been exposed to moisture. 
See that the fuse is properly coiled close to the hole before 
blasting, in order that it may not be torn out by blasts from a 
neighboring hole. Instruct the men in the proper way to 
prepare a primer. See that the fuse is cut squarely; that an 
inch or so of it is discarded; that the grains of powder do not 
leak out of the end that is inserted into the detonator; that the 
crimping is done carefully with the proper tool; that the detona- 
tor is not buried too deeply in the dynamite, and that caps 
of sufficient strength are used. 



SAFETY 323 

Always count the holes as they are blasted, and never fail 
to inspect the new face for evidences of missed holes. See that 
any such are detonated properly as soon as they are discovered, 
even at the possible cost of some delay. Insist that the shovel- 
ers use their picks properly when picking down the muck pile. 
Keep a close watch for any unexploded dynamite in the muck, 
and have the men do likewise; when such is found, remove it 
carefully to a place of safety and be particularly cautious when a 
piece of fuse accompanies it. Never start a new hole in the 
remains of one that has ever held dynamite. 

When the presence of any amount of dangerous gases, either 
from explosives or from natural sources, is suspected, see that 
the men are supplied with fresh air either by opening the com- 
pressed-air line or by breaking into the ventilating pipe, if the 
current is in the right direction. Do not willingly remain 
or permit the men to remain in any atmosphere that will not 
support a candle-flame, because there is no way to tell how bad 
it may be getting after the light becomes extinguished, although 
a man can exist for some time in such an atmosphere. See 
that the men do not use anything but safety lamps or their 
equivalent in tunnels where explosive gases are encountered, 
and do not permit any means of striking an open light to be 
carried into such a tunnel. 

Have the track and road-bed kept in as good condition as 
possible in order to lessen the risk of derailments. Do not 
permit men to ride upon loaded trains unless it is absolutely 
necessary, and in such cases warn them carefully as to the risk 
being taken. Even when the men are riding in empty cars, 
insist that they keep their feet and hands inside the car and 
that they watch carefully for low places in the roof. Never 
fail to discharge any driver caught ''riding the chain." See 
that the men give an approaching train of cars plenty of room, 
and, if animals are used to draw them, see that the men hide 
their lights when the animals approach. 

Warn the men of the danger from the trolley wire. Familiar- 
ize yourself with the proper means of resuscitation after an 
electrical shock. See that the men are not permitted to carry 



324 MODERN TUNNELING 

on their shoulders tools or other instruments that are con- 
ductors of electricity. Inspect regularly any cables or wires 
for carrying electricity to lights in the heading, or any others 
that have to be moved frequently, and see that all worn parts 
are covered with insuL-^ting material or replaced if necessary. 
Do not permit the men to ride on electric locomotives. 

See that no piles of combustible rubbish are allowed to 
accumulate underground, and do not permit the use of candles 
or torches in the vicinity of hay or other inflammable sub- 
stances. Do not fail to discharge any men guilty of leaving 
candles or torches burning near timbers, and especially of 
wedging a candle between two nails driven into a post. 

Exercise special precautions when approaching a place 
where an inrush of water is to be expected. 

Be particularly cautious about drunkenness. Note the men 
when coming on shift and do not permit even slightly intoxicated 
men underground; if such a man is discovered in the tunnel, 
send him to the surface at once. Discharge those who are 
habitual offenders in this respect. 

Precautions eor the Miner 

Do not return to the face of the tunnel without testing the 
newly exposed roof for loose rocks, and if any such are discovered 
either clean them down yourself or report them to the foreman. 
Form the habit of carefully examining the roof as you pass in 
and out of the tunnel, testing doubtful places for vibration; call 
the foreman's attention at once to any ground that you think 
should be timbered or to any timbers that need reheving to 
prevent their breaking. 

If you are called upon to use dynamite, do so with great care, 
obc3rving the precautions outlined in previous paragraphs. 
Never attempt to scare any one by reckless handling of explo- 
sives, and never treat dynamite with roughness or rely in any 
other manner upon its not exploding. Never place or carry 
detonators or primers and the rest of the supply of dynamite for 
the round in the same box or bundle. If it is your duty to assist 
in the loading of the holes, do this with care, using pressure 



SAFETY 325 

rather than a blow to tamp the powder in the hole, and always be 
careful not to use too much force in pushing it. 

Inquire as to the rate at which the fuse burns, especially when 
a new brand is being tried, and see that the fuse is cut long 
enough to give you and your companions time to reach a place 
of safety. Protect the fuse from mechanical injury, such as 
scraping, blows, or too great pressure either from falling rocks 
or from the bar when tamping the hole; never use a fuse that 
has been thus damaged. Never reload a bore-hole before it 
has had time to cool. Do not use fuse that you know has 
been stored near a boiler, steam pipes, or other source of heat, 
or one that has been exposed to moisture. If you prepare 
the primer, see that an inch or so is cut squarely from the end 
of the fuse before it is put into the detonator; that no powder 
runs out of the end of the fuse during this process; and that 
the detonator is properly crimped around the fuse. Under 
no circumstances use anything but the regular crimping tool 
for this purpose. 

Always inspect each new face for evidences of a misfire, and 
if one is discovered, call the foreman's attention to it immedi- 
ately, so that he may have it detonated. Never attempt to 
pick out the material from such a hole; either explode it with a 
primer, or, if this cannot be done, drill and fire another hole at 
least two feet away. Use great care in removing any unexploded 
dynamite from the muck pile and be especially cautious if a 
piece of fuse is discovered near it, for this may show that there 
still is a detonator in the cartridge. Never handle a pick like a 
sledge hammer; pull or scrape the material down rather than 
strike it with the pick. Do not start a new hole in the remnants 
of a former one that has ever held dynamite, for there is always 
a chance that it may not have been detonated. 

Whenever you feel that you are inhaling fumes from dyna- 
mite that has burned, or any other harmful gases, try to get to 
fresh air as soon as possible ; the quickest way to do this is often 
to open the compressed-air line, or to break down the ventilating 
pipe if you know that the current is in the right direction. Never 
use anything but a safety lamp or its equivalent in a tunnel 



326 MODERN TUNNELING 

where explosive gases are known to exist, and do not carry any 
other means of striking a light into such a tunnel. 

Never attempt to ride upon a full car or a loaded trip; and 
when riding in an empty car see that your feet and hands are 
well inside and your head is low enough to clear the roof at all 
places. Learn which side of the tunnel has the most room and 
always take all of it you can when a trip of cars approaches. If 
it is drawn by an animal, hide any bright light you may be 
carrying. If it is your duty to drive a horse or mule or to run a 
locomotive, try to do everything possible to prevent derailments; 
report any places where the track or road-bed is in bad condition. 
Remember that the front end of the trip is the most dangerous 
place you can occupy, so that if this is necessary, you must take 
extra care; never under any circumstances ride with one foot on 
the chain by which the cars are being pulled. Take care that 
the animal does not step on you or kick you, and speak to him 
before approaching him from the rear. In placing a derailed 
loaded car back upon the rails, take care not to strain or other- 
wise injure yourself in so doing; keep your feet and hands in a 
safe position and see that the car does not topple over and crush 
you against the sides of the tunnel. 

Bear constantly in mind that the trolley wire is dangerous, 
and that you must pass within a few inches of it when going in 
and out of the tunnel, often when your attention must be given 
to your footing. This is especially true when you climb into cars. 
Never carry on your shoulders, when in a tunnel where there is a 
trolley wire, tools or drill steel or anything else that is of metal 
or wet. Do not handle any electrical equipment unnecessarily, 
nor ride on electric locomotives. Never cause any one to receive 
an electric shock; it is never possible to foretell its results. If it 
is your duty to repair electrical apparatus, see that you are prop- 
erly insulated, or that the current is cut off and cannot be turned 
on without your knowledge; keep your hands and body in such 
a position that a recoil from an accidental shock will throw you 
clear of any charged part of the apparatus. In removing and 
replacing the temporary cluster of electric Hghts in the heading, 
be careful not to touch any bare or injured place in the wires and 



SAFETY 327 

call the foreman's attention to any damaged place you may 
discover. Familiarize yourself with the methods of reviving a 
person injured by electric shock, and put them into practice as 
soon as possible, whenever necessity occurs. 

Do not smoke or throw a lighted match near any pile of inflam- 
mable rubbish either in a building or near timbering, and do not 
carry a candle or a toroh near any piles of hay. Never wedge a 
candle between two nails on a post or other piece of timber; 
many disastrous mine fires have started in just this way. 

Never take a drink of liquor before or during working hours, 
and do not hesitate to report any man you see doing so or who is 
in an intoxicated condition; your safety and perhaps your life 
may be sacrificed to his carelessness when under the influence 
of liquor. 



CHAPTER XVI 
COST OF TUNNEL WORK 

From the viewpoint of publicity, the cost of tunnehng is per- 
haps the most neglected feature of the work. Although the last 
ten or fifteen years have witnessed a very considerable amount 
of tunnel driving, and there is presumably a large amount of 
cost data in existence, and although the articles describing 
methods, equipment, and other features of many of these tunnels 
have been numerous, only very few data regarding the cost 
of the work, which is a very practical means by which the 
efhcacy of methods and equipment can be measured, have 
found their way into the ordinary channels of publicity — the 
engineering periodicals. This is possibly due in part to the 
prejudice entertained by some contractors and tunnel men 
against a publication of their cost data; in other cases the men 
actually do not know what the work has cost them, aside per- 
haps from the difference between their bank account at the 
beginning and at the end of the job; while others possibly are 
unwilling to go to the trouble (for it does involve extra labor) 
of preparing such matter for the magazines or other publica- 
tions. 

In an attempt to remedy this condition somewhat, there are 
set forth on the following pages as complete and accurate data 
as could be obtained, showing the cost of various phases of 
tunnel work at a number of different tunnels. Although the 
writers have not had the advantage of auditing the books from 
v/hich these figures were taken, and hence cannot vouch per- 
sonally for the absolute accuracy of the figures, the data were 
in all cases secured from persons in charge or those who were in a 
position to know what the work actually cost. Accompanying 
the figures is a brief hst of the more important features of the 
tunnel, without which it is impossible to make even an ap- 
proximate comparison between any two pieces of tunnel work. 

328 



COST OF TUNNEL WORK 



329 



CORONADO TUNNEL 

Location: Metcalf, Arizona. 

Purpose: Mine development and transportation. 

Cross section: Square. 

Size: 9 by 9 feet. 

Length: 6,300 feet. 

Rock: Granite and porphyry. 

Type of power: Steam, with crude oil as fuel 

Ventilation: Pressure blower. 

Size of ventilating pipe: 12 inches. 

Drills: 3 pneumatic piston drills for the first half of the tunnel, 

3 pneumatic hammer drills for the last half. 
Mounting of drills: Horizontal bar. 

Number of holes per round: 21 in granite, 17 in porphyry. 
Average depth of round: 6 feet. 

Number of drillers and helpers per shift : 3 drillers, i helper. 
Number of drill shifts per day: 3. 

Explosives: 60 per cent, and 100 per cent, gelatine dynamite. 
Number of muckers per shift: 4 to 6. 
Number of mucking shifts per day: 3. 
Type of haulage : Mules. 

Maximum progress in any calendar month: 606 feet, June, 19 13. 
Average monthly progress: Approximately 415 feet. 

COST OF DRIVING CORONADO TUNNEL 



Month 



Footage Labor Supplies 



Total 



June, 1912 . . . 

July 

August 

September . . . 

October 

November . . . 
December . . . 

January, 19 13 
February .... 

March 

April 

May 

June 

July 

August 

Average . . . 




S29.04 
15.88 
13.22 
21.60 
22.47 
28.24 
25.60 

35-82 
28.24 
21.79 
23.12 

2599 
21.30 
21.84 

18.52 



$22.64 



330 MODERN TUNNELING 

DETAILED COSTS, CORONADO TUNNEL 
5,799 Feet 

Labor ^°o?T^Snn^er 

Machine men $2,918 

Mucking ^ 3.399 

Tramming and dumping i . 001 

Power-house o . 791 

Track and temporary timbering o . 485 

■ Tool-dressing o . 461 

Supervision o . 334 

Repairs to equipment 0.625 

Equipment installation i . 740 

General o • 756 

Total labor $13 • 512 $13 . 512 

Supplies 

Explosives $2 . 820 

Fuel oil 2 . 280 

Drill parts 0.612 

Stock feed o . 185 

Water o. 195 

Temporary timber o . 330 

Candles and carbide ^ o . 150 

Car repair parts o. 095 

Electrical supplies o. 143 

Blacksmith coal o . 100 

Lubricants 0.158 

Iron, sheet steel, etc 0.123 

Belting, hose, etc 0.127 

Building material o . 148 

Drill steel o. 290 

Miscellaneous 0.357 

Total supplies $8. 124 $8. 124 

Depreciation 

Machine drills (50%) $0. 274 

Track material (25%) o . 240 

Pipe and fittings (50%) o. 388 

Drill-sharpener (25%) 0.039 

Pumps (25%) o.oii 



COST OF TUNNEL WORK 331 

Depreciation 

Motors and blowers (25%) $0,030 

Compressor (5%) 0.013 

Boilers (5%) 0.013 

Total depreciation $1 . 008 $1 . 008 

Total average cost of tunnel $22 . 64 

GUNNISON TUNNEL 

Location: Montrose, Colorado. 

Purpose: Irrigation and reclamation. 

Cross-section: Horse-shoe. 

Size: 10 feet wide at the bottom; 10 feet 6 inches wide at the spring 

line; 10 feet high at the spring line; 12 feet 4 inches high at the 

center of the arch. 
Length: 30,645 feet. 
Rock: Chiefly metamorphosed granite with some water-bearing 'clay 

and gravel, some hard black shale, and a zone of faulted and broken 

material. 
Type of power: Steam. 
Ventilator: Pressure blower. 
Size of ventilating pipe: 17 inches. 

Drills: Pneumatic, hammer at first, four drills in the heading; pneu- 
matic, piston to finish, four drills in the heading. 
Mounting of drills: Horizontal bar for the hammer drills; vertical 

columns for the piston drills. 
Number of holes per round: 20 to 24 in the heading (approximately 

one-half of the tunnel). 
Average depth of round: 6 to 7 feet. 

Number of drillers and helpers per shift: 4 drillers and 2 helpers. 
Number of drill shifts per day: 3. 

Explosive: 60 per cent, gelatin dynamite, with some 40 per cent. 
Number of muckers per shift: 5 to 8. 
Number of mucking shifts per day: 3. 
Type of haulage: Electric. 
Wages: Drillers, $3.50 and $4.00; helpers, $3.00 and $3.50; muckers, 

$2.50 and $3.00; blacksmiths, $3.50 and $4.00; motormen, $3.00; 

brakemen, $2.50 and $3.00; power engineers, $4.00. 
Maximum progress in any calendar month: 449 feet. 
Average monthly progress: 250 feet, approximately. 



332 MODERN TUNNELING 

COST OF DRIVING THE GUNNISON TUNNEL 

Cost per Foot 
of Tunnel 

10,019 f^et driven by undercut heading and subsequent 

enlargement $87 . 23 

20,626 feet driven by top heading and bench 62 . 18 

Average cost of excavation of entire tunnel $70 . 66 

These costs include all labor, all materials, all repairs, all power, 
depreciation figured as 100 per cent, on all equipment, with a pro- 
portionate charge for general (supervisory) and miscellaneous ex- 
penses of the entire reclamation project. 

LARAMIE-POUDRE TUNNEL 

Location: Home, Colorado. 

Purpose: Irrigation. 

Cross-section: Rectangular. 

Size: ()% feet wide by 7^ feet high. 

Length: 11,306 feet. 

Rock: Close-grained red and gray granite. 

Type of power: Hydraulic at the east end, electric at the west. 

Ventilator: Pressure blower. 

Size of ventilating pipe: 14 and 15 inches. 

Drills: 3, pneumatic hammer. 

Mounting of drills: Horizontal bar. 

Number of holes per round: 21 to 23. 

Average depth of round: 10 feet at first; 7 to 8 feet later. 

Number of drillers and helpers per shift: 3 drillers, 2 helpers. 

Number of drill shifts per day: 3. 

Explosive: 60 per cent, gelatine dynamite, with some 100 per cent, in 
the cut holes. 

Number of muckers per shift: 6. 

Number of mucking shifts per day: 3. 

Type of haulage : Mules. 

Wages: Drillers, $4.50; helpers, $4.00; muckers, $3.50; blacksmiths, 
$5.00; drivers, $4.50; dumpmen, $3.50. 

Maximum progress in any calendar month: 653 feet, March, 191 1. 

Average monthly progress: 509 feet (for the 16 months when complete 
plant operated). 

Special features: Inaccessibility; the tunnel was located about 60 
miles from the nearest railroad siding and the roads were moun- 
tainous and very steep in places. 



COST OF TUNNEL WORK 333 

COST OF DRIVING THE LARAMIE-POUDRE TUNNEL 
11,306 Feet 



Per Foot of 
Tunnel 



Superintendents and foremen $1 

Drilling 4 

Mucking and loading 4 

Tramming and dumping 4 

Track and pipe 

Power house 

Blacksmithing '. 

Repairs 

Bonus to workmen i 

Maintenance of camps, buildings, and fuel 

Machinery repairs 

Air drills and parts i 

Picks, shovels, and steel 

Explosives 4 

Lamps and candles 

Oil and waste ; . . 

Blacksmith supplies 

Liability insurance 

Office supplies, telephone, and bookkeeping 



$29 
Permanent equipment (less approx. 10 per cent, salvage) .... 9 



50 
47 
92 

63 
47 
35 
84 
47 
75 
62 
12 

33 
84 

50 
42 

38 

53 
81 
86 



$39-54 



The permanent equipment included power plant, camp buildings 
and furnishing, pipes, rails, etc. 

LOS ANGELES AQUEDUCT 
Little Lake Division, Tunnels i to ioa 

Location: Inyo County, CaUfornia. 

Purpose: Water supply, power, and irrigation. 

Cross-section: See Figure 6, p. 41. 

Size: See Figure 6, p. 41. 

Type of power: Electric power purchased at a nominal cost per kilo- 
watt-hour from a hydraulic plant constructed and owned by the 
acqueduct. 

Ventilators: Pressure blowers. 



334 MODERN TUNNELING 

Size of ventilating pipe: 12 inches. 

Drills: Pneumatic hammer, usually 2 in each heading. 

Mounting of drills : Horizontal bar. 

Number of holes per round: Usually 14 to 16. 

Average depth of round: 6 to 10 feet. 

Number of drillers and helpers per shift: 2 drillers and 2 helpers. 

Number of drill shifts per day: Usually i, but sometimes 2. 

Explosive: 40 per cent, gelatine dynamite, with some 20 per cent, and 

some 60 per cent. Ammonia dynamite also tried. 
Number of muckers per shift: Usually 5. 
Number of mucking shifts per day: i usually, but 2 when 2 drill-shifts 

were employed. 
Type of haulage: Tunnels i to 5N, mules; tunnels 3S to loAN, 

electric; tunnel loAS, mules. 
Wages: Drillers and helpers, $3.00; muckers, I2.50; blacksmiths, 

$4.00; helpers, $2.50; motormen, $2.75; dumpmen, $2.50. 

COST OF DRIVING TUNNEL i-B-S, 1,341 FEET 

Driven through medium hard granite at an average speed of 225 
feet per month* 

Cost per Foot 
of Tunnel 

Excavation ■ I9 • 1 5 

Engineering .18 

Adit proportion .28 

Permanent equipment (estimated) 2. 35 

Timbering (857 feet) i . 02 

$12.98 

In this tunnel, as in all of the tunnels of this division and of the 
Grapevine division, the cost of excavation includes the wages of the 
following: Shift foremen, drillers, helpers, muckers, motormen or 
mule drivers, dumpmen, blacksmiths and helpers, machinists, elec- 
tricians (part) , and power engineers. 

It also includes the cost of the following supplies: Powder, fuse, 
caps, candles, light globes, machine oil, blacksmith supplies and fuel, 
and machinists' supplies. 

It also includes the cost of power and of repairs for power, haulage, 
compressor, and ventilating machinery. 

''Engineering" includes the cost of giving line and grade, etc. 

* The average speed given is computed on the basis of one heading per 
month. 



COST OF TUNNEL WORK 335 

*'Adit proportion'* is a proportionate charge per foot of tunnel 
to defray the cost of an adit from the surface to the tunnel line. 

" Permanent equipment " costs were not segregated for each tunnel, 
but were compiled for the whole division, so that the charge repre- 
sents a proportionate charge per foot for the entire division cost, 
without salvage, of the following: Trolley and light lines, including 
freight and cost of installation; pressure air lines with freight and in- 
stallation; ventilating Hnes with freight and installation; water Unes 
with freight and installation; mine locomotives and cars, picks, 
shovels, drills and drill-sharpeners, with repairs for the last four items. 

COST OF DRIVING TUNNEL 2, 1,739 FEET 
Driven through medium granite, but very wet, at an average speed of 

170 feet per month. Cost per Foot 

' ^ of Tunnel 

Excavation $8.81 

Engineering 19 

Adit proportion 34 

Permanent equipment 2.35 

Timbering (1,590 feet) 3 . 28 



$14-97 

COST OF DRIVING TUNNEL 2-A, 1,322 FEET 
Driven through medium granite at an average speed of 150 feet 

per month. Cost per Foot 

^ of Tunnel 

Excavation $8 . 05 

Engineering 16 

Adit proportion 34 

Permanent equipment 2.35 

Timbering (1,322 feet) 2.51 



$13-41 



COST OF DRIVING TUNNEL 3-N, 1,148 FEET 
Driven through medium hard granite at an average speed of 150 

feet per month. Cost per Foot 

■^ of Tunnel 

Excavation $10 . 00 

Engineering 23 

Adit proportion 51 

Permanent equipment 2.35 

Timbering (956 feet) 2 . 44 

$15.53 



336 MODERN TUNNELING 



COST OF DRIVING TUNNEL 3-S, 1,358 FEET 

Driven through granite of variable hardness, and containing pockets 
of carbon dioxide gas, at an average speed of 155 feet per month. 

Cost per Foot 
of Tunnel 

Excavation $12.38 

Engineering 28 

Adit proportion 16 

Permanent equipment 2.35 

Timbering (1,244 feet) 3 . 28 

$18.45 

COST OF DRIVING TUNNEL 3 COMPLETE (3 N AND 3 S) 
4,044 FEET 

Driven through decomposed granite of medium hardness, dissected 
by sHps and talcose planes requiring timber where ground was 
wet, and also containing pockets of carbon dioxide gas, making 
work difhcult and requiring extra provisions for ventilation. 
Average speed, 140 feet per month. 

Cost per Foot 
of Tunnel 

Excavation $12.67 

Engineering 24 

Adit proportion 35 

Permanent equipment 2.35 

Timbering (3,570 feet) 2.71 

$18.32 

COST OF DRIVING TUNNEL 4, 2,033 FEET 

Driven through medium to hard granite at an average speed of 145 

feet per month 

Cost per Foot 
of Tunnel 

Excavation $1 2 . 00 

Engineering 24 

Adit proportion 16 

Permanent equipment 2.35 

Timbering (1,705 feet) 2.16 

$16.91 



COST OF TUNNEL WORK 337 



COST OF DRIVING TUNNEL 5, 1,178 FEET 

Driven through medium to very hard granite at an average speed 
of 120 feet per month 

Cost per Foot 
of Tunnel 

Excavation $11.10 

Engineering 21 

Adit proportion 08 

Permanent equipment 2.35 

Timbering (916 feet) i . 83 

$15-57 



COST OF DRIVING TUNNEL 7, 3,596 FEET 

Driven through basic biotite granite of variable hardness at an 
average speed of 140 feet per month 

Cost per Foot 
of Tunnel 

Excavation $13 . 55 

Engineering 27 

Adit proportion 13 

Permanent equipment 2.35 

Timbering (2,609 feet) 3 • 60 



$19.90 



COST OF DRIVING TUNNEL 8-S, 1,334 FEET 

Driven through medium to hard granite at an average speed of 135 

feet per month 

Cost per Foot 
of Tunnel 

Excavation $12.82 

Engineering 19 

Adit proportion 18 

Permanent equipment 2.35 

Timbering (126 feet) 39 

|i5-93 



33? MODERN TUNNELING 



COST OF DRIVING TUNNEL 9, 3,506 FEET 

Driven through medium to hard granite at an average speed of 195 

, feet per month cost per Foot 

of Tunnel 

Excavation $12.19 

Engineering 18 

Adit proportion 07 

Permanent equipment 2.35 

Timbering (305 feet) 29 • 

$15.08 

COST OF DRIVING TUNNEL 10, 5,657 FEET 

Driven through medium to hard granite at an average speed of 
200 feet per month cost per Foot 

of Tunnel 

Excavation $13 . 50 



Engineering 

Permanent equipment 2 

Timbering (194 feet) 



$16 



19 
35 
II 



15 



COST OF DRIVING TUNNEL lo-A-N, 1,496 FEET 

Driven through medium to hard granite at an average speed of 165 

feet per month cost per Foot 

of Tunnel 

Excavation $13 . 02 

Engineering 13 

Permanent equipment 2.35 

Timbering (24 feet) 78 

$16.28 

COST OF DRIVING TUNNEL lo-A-S, 2,200 FEET 

Driven through medium to hard granite at an average speed of 200 

feet per month cost per Foot 

of Tunnel 

Excavation $12.37 

Engineering 20 

Permanent equipment 2.35 

Timbering (215 feet) i . 15 

$16.07 



COST OF TUNNEL WORK 339 

Grapevine Division, Tunnels 12 to 17-B 

Location: Kern County, California. 

Purpose: Water supply, power, and irrigation. 

Cross-section: See Figure 6, p. 41. 

Size: See Figure 6, p. 41. 

Type of power: Electric power purchased from aqueduct plant. 

Ventilators: Pressure blowers. 

Size of ventilating pipe: 12 inches. 

Drills: Pneumatic hammer, usually 2 in each heading. 

Mounting of drills: Horizontal bar. 

Number of holes per round: Usually 18 to 20. 

Average depth of round: 6 to 8 feet. 

Number of drillers and helpers per shift: 2 drillers and 2 helpers. 

Number of drill shifts per day: Usually 2. 

Explosive: 40 per cent, ammonia dynamite, but 60 per cent, and 75 

per cent, gelatine dynamite were employed in hard ground. 
Number of muckers per shift: 4 or 5. 
Number of mucking shifts per day: Usually 2. 
Type of haulage: Electric after the first 400 to 500 feet. 
Wages: Drillers and helpers, $3.00; muckers, $2.50; blacksmiths, 

$4.00; helpers, $2.50; motormen, $2.75; dump men, $2.50. 

COST OF DRIVING TUNNEL 12, 4,900 FEET 
Driven through hard granite at an average speed of 185 feet per 

month Cost per Foot 

of Tunnel 

Excavation* $22.10 

Engineering* 32 

Permanent equipment 2.25 

Timbering (90 feet) 08 

$24.75 

COST OF DRIVING TUNNEL 13, 1,525 FEET 
Driven through hard granite at an average speed of 130 feet per 

month Cost per Foot 

of Tunnel 

Excavation ' $20 . 60 

Engineering 10 

Permanent equipment 2.25 

Adit proportion 37 

$23.32 

* These items include the same costs as for the Little Lake division, see 
page 334. 



340 MODERN TUNNELING 



COST OF DRIVING TUNNEL 14, 859 FEET 



Cost per Foot 
of Tunnel 



70 



Excavation $22 

Engineering 

Permanent equipment 2 

Adit proportion 

Timbering (22 feet) , 



13 
25 
72 
16 



$25.96 



COST OF DRIVING TUNNEL 15, 895 FEET 



Cost per Foot 
of T«nnel 



Excavation $23 . 28 

Engineering 11 

Permanent equipment 2.25 

Adit proportion 2.42 



$28.06' 

COST OF DRIVING TUNNEL 16, 2,723 FEET 

Driven through hard granite at an average speed of 145 feet per 

month 

Cost per Foot 
of Tunnel 

Excavation $20 . 07 

Engineering ■. 17 

Permanent equipment 2.25 

Adit proportion 55 

Timbering (18 feet) 04 



$23.08 



COST OF DRIVING TUNNEL 17, 3,024 FEET 

Cost per Foot 
of Tunnel 

Excavation $20 . 47 

Engineering 21 

Permanent equipment 2.25 

Timbering (142 feet) 22 

$23-15 



COST OF TUNNEL WORK 341 

COST OF DRIVING TUNNEL 173^^, i,345 FEET 
Driven through medium to hard granite at an average speed of 
225 feet per month 

Cost per Foot 
of Tunnel 

Excavation $19 . 56 

Engineering 31 

Permanent equipment 2.25 

$22.12 

COST OF DRIVING TUNNEL 17-A, 3,275 FEET 

Cost per Foot 
of Tunnel 

Excavation $18 . 70 

Engineering 17 

Permanent equipment 2.25 

Timbering (441 feet) i . 18 

$22.30 

COST OF DRIVING TUNNEL 17-B, 4,915 FEET 

Cost per Foot 
of Tunnel 

Excavation $2 1 . 09 

Engineering 21 

Permanent equipment 2.25 

Timbering (163 feet) i . 90 

$25.45 
Elizabeth Lake Division, 

ELIZABETH TUNNEL 

Location: Los Angeles County, CaHfornia. 
Purpose: Water supply, power, and irrigation. 
Cross-section: See Figure 6, p. 41. 
Size: See Figure 6, p. 41. 
Length: 26,870 feet. 

Type of power : Electric power purchased from aqueduct plant. 
Ventilator: Pressure blower. 
Size of ventilating pipe: 18 inches. 

Drills: Pneumatic hammer, 3 in the south heading and 2 in the north. 
Mounting of drills: Horizontal bar. 

Number of holes per round: 25 in the south heading; 16 in the north 
heading. 



342 MODERN TUNNELING 

Average depth of round: 8 to lo feet. 

Number of drillers and helpers per shift: 2 drillers and 2 helpers at 

the north end; 3 drillers and 3 helpers at the south end. 
Number of drill shifts per day: 3. 

Explosive: 40 per cent, and 60 per cent, gelatine dynamite. 
Number of muckers per shift: 6. 
Number of mucking shifts per day: 3. 
Type of haulage: Electric. 
Wages: Drillers and helpers, $3.00; muckers, $2.50; blacksmiths, 

$4.00; helpers, $2.50; motormen, $2.75; dumpmen, $2.50. 
Maximum progress in any calendar month: 604 feet, April, 1910. 
Average monthly progress per heading: 350 feet per month. 

COST OF DRIVING THE NORTH HEADING, ELIZABETH TUNNEL 
Driven through altered granite requiring much timbering' 

1 3 » 3 70 fee t Cost per Foot 

^'^' of Tunnel 



I 



Drilling and blasting $11 

Mucking and tramming 11 

Engineering and superintendence i 

Drainage 

Ventilation 

Light and power 5 

Timbering (13,031 feet) 8 

Cost of auxiliary shaft 

Permanent equipment (full charge, no salvage — 
estimated) 3 



25 
70 
27 

45 
22 

55 
48 

93 
70 



$43-55 

COST OF DRIVING THE SOUTH HEADING, ELIZABETH TUNNEL 
Driven through medium to hard granite requiring but little timbering' 

I T, , c;00 feet Cost per Foot 

^'"^ of Tunnel 

Drilling and blasting $14.65 

Mucking and tramming 1 1 . 10 

Engineering and superintendence 86 

Drainage 17 

Ventilation 41 

Light and power 4 . 93 

Permanent equipment (without salvage — es- 
timated) 3 • 70 

Timbering (3,424 feet) 2.19 

$38.01 



COST OF TUNNEL WORK 343 



LUCANIA TUNNEL 

Location: Idaho Springs, Colorado. 

Purpose: Mine development and transportation. 

Cross-section : Square. 

Size: 8 feet by 8 feet. 

Length: 6,385 feet. 

Rock: Hard granite. 

Type of power : Purchased electric current- 

Ventilator: Pressure blower. 

Size of ventilating pipe: 18 and 19 inches. 

Drills: Pneumatic hammer, 3 in the heading. 

Mounting of drills : Vertical columns. 

Number of holes per round: 25. 

Average depth of round: 8 to 9 feet. 

Number of drillers and helpers per shift: 3 drillers and 2 helpers. 

Number of drilling shifts per day: i. 

Explosive: 50 per cent, gelatine dynamite. 

Number of muckers per shift: 3. 

Number of mucking shifts per day: i. 

Type of haulage: Horses. 

Wages: Head driller, $5.00; drillers, $4.00; nipper, $3.50; boss mucker, 

$5.00; muckers, $4.00; drivers, $4.00; power engineers, $4.00; 

blacksmith, $5.00. 
Maximum progress in any calendar month: 263 feet, September, 191 1. 
Average monthly progress: 125 feet per month for the first 4,800 

feet; 240 feet per month for the last 1,575 feet. 

AVERAGE COST OF DRIVING THE LUCANIA TUNNEL 
First 4,800 feet 

Cost per Foot 
of Tunnel 

Labor $8 . 86 

Powder 7 . 86 

Fuse and caps 17 

Candles and oil 21 

Horse feed and shoeing 18 

Power 1 . 64 

Repairs 14 

Timnel equipment 2.75 

Surface plant 1.25 



$23.06 



344 MODERN TUNNELING 

*' Tunnel equipment" includes the cost of materials and installa- 
tion of the pressure air line, the ventilating line, rails, ties and fittings, 
and the drainage ditch. 

"Surface plant" includes buildings, compressor, blower, trans- 
formers, motors, and drill-sharpener. 



AVERAGE COST OF DRIVING THE LAST i,575 FEET 

The contractor received $21.50 per foot to cover the cost of labor, 
powder, fuse, caps, candles, oil, horse feed and shoeing, power and 
repairs, and the installation of the timnel equipment. 



MARSHALL-RUSSELL TUNNEL 

Location: Empire, Colorado. 

Purpose: Mine drainage, development, and transportation. 

Cross-section: Square. 

Size: 8 feet by 8 feet. 

Length: 11,000 feet projected; 6,700 feet driven, January i, 1913. 

Rock: Granite and gneiss. 

Type of power: Purchased electric current; also a small auxiliary 

hydraulic plant. 
Ventilator: Fan. 

Size of ventilating pipe: 12 and 13 inches. 
Drills: 2, pneumatic hammer. 
Mounting of drills : Vertical columns. 
Number of holes per round: 18 to 20. 
Average depth of round: 9 to 10 feet. 

Number of drillers and helpers per shift: 2 drillers and 2 helpers. 
Number of drill shifts per day: i. 

Explosive : 40 per cent, gelatine dynamite with some 80 per cent. 
Number of muckers per shift: 4. 
Number of mucking shifts per day: i. 
Type of haulage: Horses. 
Wages: Drillers, $4.00; helpers, $3.00; blacksmiths, $4.00; helpers, 

$3.00; muckers, $3.25; trammers, $3.75; dumpmen, $3.25; power 

engineer, $3.50; shooters, $3.25. 
Maximum progress for any calendar month: 187 feet, June, 1909. 
Average monthly progress: 125 feet. 



, 



COST OF TUNNEL WORK 345 

COST OF DRIVING THE MARSHALL-RUSSELL TUNNEL 
6,700 Feet 

Cost per Foot 
of Tunnel 

Labor $9.37 

Powder, fuse, caps, and blacksmith coal 3 . 35 

Drills, steel, and repairs (less 30 per cent, salvage) i . 34 

Power 1 . 41 

Permahent equipment and general expense (less 
30 per cent, salvage on permanent equipment) 3.41 

$18.88 



MISSION TUNNEL 

Location: Santa Barbara, California. 

Purpose: Water supply. 

Cross-section : Trapezoid. 

Size: 6 feet wide at the base; 4>^ feet wide at the top; 7 feet high. 

Length: 19,560 feet. 

Pock: Shale, slate, and hard sandstone. 

Ventilator: Pressure blower. 

Size of ventilating pipe : 10 inches. 

Drills: i, pneumatic hammer. 

Mounting of drills: Horizontal bar. 

Number of holes per round: 12 to 14. 

Average depth of round: 7 to 8 feet. 

Number of drillers and helpers per shift: i. 

Number of drilling shifts per day: 3. 

Explosive: 40 per cent, and 60 per cent, gelatine dynamite. 

Number of muckers per shift : 4. 

Number of mucking shifts per day: 3. 

Type of haulage : Electric. 

Wages: Drillers, $3.50; helpers, $3.00; muckers, $2.75; blacksmiths, 

$4.00; helper, $3.00; motormen, $2.75; dumpmen, $2.50; power 

engineers, $2.75. 
Maximum progress in any calendar month: 414 feet, February, 191 1. 
Average monthly progress: 210 feet. 



346 MODERN TUNNELING 



COST OF DRIVING THE SOUTH PORTAL, MISSION TUNNEL 

May, 1909, to September, 191 1 
5,515 Feet 

Cost per Foot 
of Tunnel 

Administration* $1.14 

Labor 9 . 20 

Power 2.12 

Explosives 1.97 

Timbering (563 feet) 30 

Track and pipe 1.22 

Miscellaneous suppliesf 2 . 46 

Drill parts (including steel) 1.02 

Bonus .48 



$19.91 
NEWHOUSE TUNNEL 

Location: Idaho Springs, Colorado. 

Purpose: Drainage and transportation. 

Cross-section : Square. 

Size : 8 feet by 8 feet. 

Length: 22,000 feet. 

Rock: Idaho Springs gneiss. 

Type of power: Purchased electric current. 

Ventilator: Pressure blower. 

Size of ventilating pipe : 18 inches. 

Drills: Pneumatic hammer. 

Mounting of drills: Vertical column. 

Number of holes per round: 14 to 22. 

Number of drill shifts per day: i and 2. 

Explosive: 40 per cent, gelatine dynamite, with some 100 per cent. 

in the cut holes. 
Number of muckers per shift: 3. 
Number of mucking shifts per day: i and 2. 
Type of haulage : Electric. 
Wages: Drillers, $4.00 to $4.50; helpers, $3.25 to $4.00; muckers, 

$3.50; motormen, $3.50; dumpmen, $3.00; blacksmiths, $3.50 to 

$4.50; helpers, $3.00. 

* Includes superintendence, office supplies, and general charges, 
t Includes candles, light globes, shovels, picks, blacksmiths' supplies and 
fuel, and machinists' supplies. 



COST OF TUNNEL WORK 
COST OF DRIVING THE NEWHOUSE TUNNEL 



347 





Jan. to Aug. 

1909 

2,233 feet 


Sept. to Dec. 

1909 

1.098 feet 


April to Aug. 

1910 

693 feet 


Labor 


$6.72 

4-15 
•39 

1.49 
1.99 
1-57 

1.50 

1.74 
•79 


$6.98 

3-52 

•36 

1.47 
2.16 
2.61 

2.74 

1.78 
.80 


$ii^73 

4.57 

•44 

2.22 
2.82 
2.00 

2.86 

2.19 
1.85 


Explosives 


Fuse and caps 


Transportation of broken 
rock 

Power 

Blacksmithing 

Use of drills, repairs, and 
steel 

Equipment, ties, rails, pipe, 
etc. 

Sundries 






$20.34 


$22.42 


$30.68 



RAWLEY TUNNEL 

Location: Bonanza, Colorado. 

Purpose: Mine drainage and development. 

Cross-section : TrapezoidaL 

Size: 8 feet wide at the base; 7 feet wide at the top; 7 feet high. 

Length: 6,235 feet. 

Rock: Tough hard andesite. 

Type of power: Steam with wood for fueL 

Ventilator: Pressure blower. 

Size of ventilating pipe: 12 and 13 inches. 

Drills: 2, pneumatic hammer. 

Mounting of drills: Horizontal bar. 

Number of holes per round: 23 to 25. 

Average depth of round: 8 to 9 feet at first; 5 to 6 feet later. 

Number of drillers and helpers per shift: 2 drillers and 2 helpers. 

Number of drill shifts per day: 2 at first; 3 later. 

Explosive: 40 per cent, and 60 per cent, gelatine dynamite (in the 

proportion of about 2 to i). 
Number of muckers per shift: 4. 
Number of mucking shifts per day: 2 and 3. 
Type of haulage: Horses and mules. 
Wages: Drillers, $4.50; helpers, $3.75; muckers, $3.50; blacksmiths, 

$4.50; drivers, $4.50; power engineers, $4.00. 
Maximum progress in any calendar month: 585 feet, July, 191 2. 
Average monthly progress: Approximately 350 feet. 



348 MODERN TUNNELING 

COST OF DRIVING RAWLEY TUNNEL 
6,235 Feet * 

Cost per Foot 
of Tunnel 

Drilling and firing $5.25 

Mucking 2.16 

Tramming i . 13 

Track and pipe 44 

Miscellaneous underground expenses i . 44 

Power plant 2 . 50 

Blacksmithing 73 

Miscellaneous surface work 83 

General expenses i . 98 

Permanent plant 3 . 24 

Timbering (1,618 feet) i . 18 

Boarding-house, debit balance 04 

$20.92 
Credit by salvage on permanent plant i.ii 

$19.81 

*' Drilling and firing" includes labor, powder, fuse, caps, supplies, 
and repairs. ''Mucking," "tramming," and "track and pipe" in- 
clude labor and supplies. "Miscellaneous underground expenses" 
includes wages of foremen, underground telephone, etc. "Power 
plant" includes labor, supplies, and fuel. "Blacksmithing" and 
"Miscellaneous surface work" include labor and supplies. "General 
expenses" include salaries, office supplies, telephone, etc. "Per- 
manent plant" includes machinery and buildings, with labor of 
installation, steel rails, permanent supplies, and repairs. "Timbering" 
includes labor and supplies. The salvage on the permanent plant 
is approximately 50 per cent, on salable articles, such as machinery, 
rails, cars, etc. 

ROOSEVELT TUNNEL 

Location: Cripple Creek, Colorado. 

Purpose: Mine drainage. 

Cross-section: Rectangular, with large ditch at the side. 

Size: 10 feet wide by 6 feet high. 

* A more detailed statement of the cost of this tunnel may be found in 
Trans. Am. Inst. Mining Engineers, February meeting, 1913. 



COST OF TUNNEL WORK 349 

Length: 15,700 feet. 

Rock: Pike's Peak granite, chiefly. 

Type of power: Purchased electric current. 

Ventilator: Pressure blower. 

Size of ventilating pipe: 16 and 17 inches. 

Drills: 3, pneumatic hammer. 

Mounting of drills : Horizontal bar. 

Number of holes per round: 24, usually. 

Average depth of round: 6 to 7 feet. 

Number of drillers and helpers per shift: 3 drillers; 2 helpers. 

Number of drill shifts per day: 3. 

Explosive: 40 per cent., 60 per cent., and some 100 per cent, gelatine 
dynamite. 

Number of muckers per shift: 4, usually. 

Number of mucking shifts per day: 3. 

Type of haulage: Horses and mules. 

Wages: Drillers, $5.00; helpers, $4.00; muckers, $3.50; power en- 
gineer, $4.00; blacksmith, $5.00; helper, $3.50; dumpman, $3.50; 
drivers, inside, $5.00; outside, $4.00. 

Maximum progress in any calendar month: 435 feet, portal heading, 
January, 1909. 

Average monthly progress: Portal heading, 300 feet; shaft headings, 
270 feet; all headings, 285 feet. 

COST OF DRIVING ROOSEVELT TUNNEL 

Total cost of portal work $111,980.06 

Contractor's percentage 11,404.88 

Cost of shaft headings 262,126.55 

Total cost of tunnel $385,511.49 

Number of feet driven I4ji67 

Average cost per foot 27.21 

COST OF DRIVING THE PORTAL HEADING 
Month Foo'age Cost per Foot 

Feb. and March, 1908 514 $22 . 690 

April 262 30 . 970 

May 268 26 . 760 

June 187 35 . 010 

July 203 29 . 600 

August 300 2 1 . 760 

September 351 19.600 

October 287 23 . 000 



350 



MODERN TUNNELING 



COST OF DRIVING THE PORTAL HEADING— ConHnued 

Month Footage Cost per Foot 

November 360 21 . 1 20 

December 334 18 . 350 

January, 1909 435 16.410 

February 290 22 . 206 

March 340 21 . 745 

April 316 21 . 266 

May 402 18 . 762 

June (8 days) 62 40. 600 



COST OF DRIVING SHAFT HEADINGS 

Month Footage 

October, 1908 (2 headings) 49 

November " 141 

December " 177 

January, 1909 " 261 

February " 601 

March " 639 

April " 670 

May " 552 

June " 498 

July (i heading) 319 

August " 410 

September " 355 

October " 380 

November " 298 

December " 251 

January, 1910 " 282 

February " 259 

March " 344 

April " 376 

May " 393 

June " 373 

July " 350 

August " 372 

September " 342 

October " 372 

November " 192 



Cost per Foot 


I105 


52 


44 


38 


40 


II 


24 


06 


23 


70 


26 


256 


25 


02 


28 


34 


27 


375 


32 


871 


27 


747 


32 


40 


28 


178 


34 


20 


35 


153 


28.82 


30 


636 


27 


62 


25-313 


24 


856 


26.616 


25 


247 


25 


029 


28 


45 


27. 


361 


27. 


786 



COST OF TUNNEL WORK 



851 



TYPICAL DISTRIBUTION OF EXPENSES 



Portal heading, July, 
203 Feet 



1908 



Cost per Foot 
of Tunnel 



Machinery and repairs $0 

Air drills and parts 

Picks, shovels, and steel i 

Ditch men i 

Explosives • 6 

Candles 

Oil and waste 

Electric power 2 

Blacksmith supplies 

General expense 

LiabiUty insurance 

Lumber ties and wedges 

Horses and feed 

Compressor men i 

Drillers and helpers 4 

Blacksmiths and helpers 3 

Muckers and drivers 4 

Foremen i 

Bookkeeper 



61 

99 
90 
09 
90 

36 
09 
06 
09 
16 

17 
01 
01 

79 
21 

43 
II 

50 
12 



$29 . 60 



TYPICAL DISTRIBUTION OF EXPENSES 

Shaft heading, February, 19 10 
259 Feet 

Cost per Foot 
of Tunnel 

Maintenance of buildings, tents, etc $0. 096 

Machinery and repairs 1158 

Air drills and parts i . 930 

Shovels, picks, and steel i . 930 

Pipe and fittings 193 

Ditch men i . 480 

Explosives 5 • 032 

Lamps and candles 217 

Oil and waste 252 

Electric power 2 . 440 

Blacksmith suppHes 150 



352 MODERN TUNNELING 

TYPICAL DISTRIBUTION OF EXPENSES— Continued 

Cost per Foot 
of Tunnel 

Liability insurance 213 

General expense 342 

Lumber, ties, and wedges 119 

Horses and feed 324 

Machine men and helpers 4 . 050 

Muckers 3 . 065 

Blacksmiths and helpers , i 362 

Engineers i . 300 

Pipe and track men 675 

Drivers and dumpmen 2 . 355 

Foremen i . 753 

Mine telephone 008 

Bookkeeper 193 



$30,636 

STILWELL TUNNEL 

Location: Telluride, Colorado. 

Purpose: Mine drainage and developmen 

Cross-section: Square with ditch at side. 

Size : 7 feet by 7 feet. 

Length: 2,950 feet. 

Rock: Conglomerate and andesite. 

Type of power: Purchased electric current. 

Ventilator: Fan. 

Size of ventilating pipe : 10 inch. 

Drills: Started with electric drills. Finished with pneumatic piston 

drills, using 2 in the heading. 
Mounting of drills : Vertical columns. 
Number of holes per round: 16. 
Average depth of round: 6 to 6}4 feet. 

Number of drillers and helpers per shift: 2 drillers and 2 helpers. 
Number of drill shifts per day: i. 
Explosive: 40 per cent, gelatine dynamite. 
Number of muckers per shift : 3. 
Number of mucking shifts per day: i. 
Type of haulage: Horses. 
Wages: Drillers, $4.50; helpers, $4.00; muckers and trammers, $3.50; 

blacksmith, $4.50. 
Maximum progress in any calendar month: 170 feet, August, 1904. 
Average monthly progress: 150 feet (last 10 months). 



COST OF TUNNEL WORK 353 

COST OF DRIVING THE STILWELL TUNNEL 



Fiscal Year 


Footage 


Cost per Foot 
of Tunnel 


1900-01 


12 feet 


$23.88 


1901-02 


490 " 


22.98 


1902-03 


377 '' 


27.94 


1903-04 


702 - 


21.69 


1904-05 


1,077 " 


21.19 


1905-06 


292 - 
2,950 feet 


30.37 




Average. $23. 38 



These costs include all labor, supplies, repairs, powder, fuse, caps, 
candles, tools, lubricants, and general expenses, and the total value 
of the electric drill plant with which the tunnel was started and the 
total value of the air drill plant which succeeded it, together with 
tunnel buildings, pipe, rails, and the ventilator, with no credit for 
salvage on any of this permanent equipment. 

The fiscal year dated from September 30. 

The tunnel was driven in 1901-02-03 mth electric drills and the 
high cost for 1905-06 was due to station cutting where the tunnel was 
double size. 

STRAWBERRY TUNNEL 

Location: Utah and Wasatch counties, Utah. 

Purpose: Irrigation and reclamation. 

Cross-section: Straight bottom and w^alls, \nth arched roof. 

Size: 8 feet ^\ide by g^ feet high. 

Length: 19,100 feet. 

Rock: Limestone mth interbedded sandstone, and sandstone with 
interbedded shale. 

Type of power: Electric power generated in a hydraulic plant operated 
in connection with the tunnel. Distance of transmission from 
west portal to power-house, approximately 23 miles. 

Ventilator: Pressure blower. 

Size of ventilating pipe: 14 inches. 

Drills: Piston pneumatic, usually 2 in the heading. 

Mounting of drills: Vertical columns. 

Number of holes per round: 16 to 18. 

Number of drillers and helpers per shift: 2 drillers and 2 helpers. 

Number of drill shifts per day: 3. 

Explosive: 40 per cent, gelatine dynamite. 

Number of muckers per shift: 6. 

Number of mucking shifts per day: 3. 



354 



MODERN TUNNELING 



Type of haulage: Electric after first 2,000 feet. 

Wages: Drillers, $3.50; helpers, $3.25; muckers, $2.75; motormen, 

$3.25; brakemen, $2.75; blacksmiths, $4.00; helpers, $2.75. 
Maximum progress in any calendar month: 500 feet, November, 1910. 
Average monthly progress: 320 feet per heading. 



COST OF DRIVING THE STRAWBERRY TUNNEL 



West heading, previous to 1909 . 16 13 feet 

during 1909 3892 " 

during 1910 5021 " 

during 191 1 3491 " 

January to July, 1912.. . 2382 " 

East " ' Oct., 191 1, to July, 191 2. 2682 " 

Average for 19,081 feet 



ost per Fo 
of Tunnel 


$60 


05 


33 


58 


30 


56 


41 


52 


36 


79 


33 


04 



$36.78 



DETAILED COST OF DRIVING THE STRAWBERRY TUNNEL, 
WEST HEADING, FOR THE YEAR 1909: 3,892 Feet 

Labor: 



Cost per Foot 
of Tunnel 



Engineering $0 

Superintendence 

Shift bosses i 

Time-keepers 

Drillmen and helpers 3 

Miners (for hand work, trimming, etc.) 

Muckers 2 

Track and dumpmen 

Mule drivers , . 

Motormen and brakemen 

Electricians and blowermen 

Disabled employees 

Timber men 

Miscellaneous 



Materials : 

Powder, fuse, caps, etc 

Lumber 

Oils, candles, etc 

Ventilating pipe 

Track, including ties 

Pressure air pipe 

Drill repair parts (including hose) 
Miscellaneous 



$3 



49 
73 
22 

36 

IS 

23 
96 

74 
39 
44 
07 

19 
22 
40 



08 

29 

22 

64 
68 
40 
18 
19 



$11.59 



5-68 



COST OF TUNNEL WORK 355 

Repairs: Cost per Foot 

Machine shop expense (including labor and ^^ Tunnel 
suppUes) So . 93 

Blacksmith shop expense (including labor and 

supplies) 1.22 

$2.15 

Power (all purposes) 7.65 

Depreciation: 

Haulage equipment $0 . 09 

General equipment i . 00 

1.09 

General expense . $3 . 96 

Camp expense 1.21 

Corral expense 25 

5-42 

Total $33.58 

"General expense" includes a proportionate charge for the ex- 
penses of the Provo ofl&ce, such as salaries, stationery, telephone, and 
supplies; also a proportionate charge for the expenses of the Wash- 
ington, the Chicago, and the Supervising Engineer's offices. The 
Provo office covers approximately 68 per cent, of this charge, the 
Washington office 23 per cent., the Chicago office 2 per cent., and 
the Supervising Engineer's office 7 per cent. 

DETAILED COST OF DRIVING THE STRAWBERRY TUNNEL, 
WEST HEADING, FOR THE YEAR 19 10: 5,021 Feet 

LaDOr. of Tunnel 

Engineering $0.61 

Superintendence 60 

Shift bosses 1.25 

Time-keepers 22 

Drillmen and helpers 2.85 

Miners 28 

Muckers 2 . 93 

Track and dumpmen 71 

Motormen and brakemen . i . 49 

Electricians and blowermen 13 

Disabled employees 16 

Timber men 28 

Miscellaneous 07 

$11.58 



356 



MODERN TUNNELING 



Materials: 

Powder, fuse, caps, etc 

Lumber 

Oils, candles, etc 

Ventilating pipe 

Track, including ties 

Pressure air pipe 

Drill repair parts (including hose) 
Miscellaneous 



Cost per Foot 
of Tunnel 

fe-52 
22 
20 
65 

74 
28 
24 

07 



Repairs : 

Machine shop expense (including labor and 

supplies) $0. 90 

Blacksmith shop expense (including labor and 

supplies) 1 . 23 



Power (all purposes) 



Depreciation : 

Haulage equipment $0. 20 

General equipment i . 00 



$5-92 



2.13 



5-70 



1.20 



General expense $332 

Camp expense 63 

Corral expense 08 



Total 



4-03 



$30.56 



DETAILED COST OF DRIVING THE STRAWBERRY TUNNEL 
WEST HEADING, FOR THE YEAR 191 1: 3,419 Feet 



Labor: 

Engineering $0 

Superintendence 

Shift bosses i 

Time-keepers 

Drillmen and helpers 4 

Miners 

Muckers 5 



Cost per Foot 
of Tunnel 



45 
82 

65 
38 
07 

37 
13 



COST OF TUNNEL WORK 



357 



Cost per Foot 
of Tunnel 



Track and dumpmen $2 . oo 

Motormen and brakemen 1.87 



Electricians and blowermen 

Disabled employees 

Timber men i 

Miscellaneous 



08 
48 
72 
05 



$19-07 



Materials: 

Powder, fuse, caps, etc $2.61 

Lumber 80 

Oils, candles, etc 43 

Ventilating pipe 77 

Track, including ties 1.52 

Pressure air pipe 36 

Drill repair parts (including hose) 34 

Miscellaneous 25 



7.08 



Repairs: 

Machine shop expense (including labor and 

supplies) $2.16 

Blacksmith shop expense (including labor and 
suppHes) 1 . 54 



Power (all purposes) 



3.70 
5.20 



Depreciation: 

Haulage equipment $1.85 

General equipment 50 



2.35 



General expense $3 . 00 

Camp expense i . 10 

Corral expense 02 



4.12 



Total 



1.52 



358 MODERN TUNNELING 

DETAILED COST OF DRIVING THE STRAWBERRY TUNNEL, 
WEST HEADING, JANUARY TO JULY, 1912: 2,382 Feet 

T 1 ' Cost per Foot 

Labor: of Tunnel 



Engineering $0 

Superintendence 

Shift bosses i 

Time-keepers 

Drillmen and helpers 3 

Miners 

Muckers 4 

Track and dumpmen i 

Motormen and brakemen , i 

Electricians and blowermen 

Disabled employees 

Timber men 2 



36 
56 
08 
26 
08 
43 
95 
55 
33 
18 
48 
59 



Materials: 

Powder, fuse, caps, etc $2.72 

Lumber 2.13 

Oils, candles, etc 32 

Ventilating pipe 70 

Track, including ties i . 51 

Pressure air pipe 30 

Drill repair parts (including hose) . .32 

Miscellaneous 39 



$16.85 



8.39 
Repairs : 

Machine shop (including labor and supplies) $1.39 

Blacksmith shop (including labor and supplies).. . 1.02 2.41 

Power (all purposes) 3.75 

Depreciation : 

Haulage equipment $2 . 20 

General equipment 50 



2.70 



General expense $1 . 90 

Camp expense 79 

2 . 69 

Total $36.79 



COST OF TUNNEL WORK 



359 



DETAILED COST OF DRIVING THE STRAWBERRY TUNNEL, 
EAST HEADING, OCTOBER, 1911, to JULY 1912: 2,682 Feet 

Labor: 



Cost per Foot 
of Tunnel 



Engineering $0 

Superintendence 

Shift bosses i 

Time-keepers 

Drillmen and helpers 3 

Muckers 4 

Track and dumpmen 2 

Mule drivers 

Timber men i 

Electricians and blowermen 

Disabled employees 

Miscellaneous 



Power (all purposes) 



Pumping (labor and material) 
Total 



49 
77 
36 

31 
62 

03 
00 

89 

80 

30 
09 
21 



Materials: 

Powder, fuse, caps, etc $2.67 

Lumber 93 

Oils, candies, etc 36 

Ventilating pipe 45 

Track, including ties 56 

Pressure air pipe 12 

Drill repair parts (including hose) ;^S 

Miscellaneous 21 



Repairs : 

Machine shop expense (labor and supplies) $0.62 

Blacksmith shop expense (labor and supplies) 65 



Depreciation : 

Haulage equipment $0.47 

General equipment 1.02 



General expenses $1 . 86 

Camp expenses 1.35 

Corral expenses 95 



$15-87 



5.68 



1.27 
3.21 



1.49 



4.16 
1.36 



$33-04 



CHAPTER XVII 
BIBLIOGRAPHY 

The following is a selected bibliography of tunneling and related 
subjects arranged by topics in chronological order. 

TUNNEL DESCRIPTIONS 

Raymond, R. W., ''The Rothschonberger Stollen," Trans. A. I. 
M. E., Vol. VI, p. 542, 1877. Full description of this 
famous old tunnel, giving its purpose, length, grade, cost, 
method of driving, rate of progress, etc. 

Anon., " Data of Tunnel Work, European," Min. Sci. Press, Vol. 
XL VIII, pp. 306-322-338. May 3, 1884, contains a descrip- 
tion of the Brandt drill and a table showing the monthly 
progress on the Arlberg tunnel. May loth gives more 
details of the drilling results. Bonus described. Also 
gives description of the use of the Brandt drill at the Son- 
stein and other places. May 17, 1884, work of the 
Brandt drill in the Pfaffensprung tunnel. Concludes with 
a statement of the advantages of the Brandt drill. 

Charton, a. Pierre, '' Arlberg Tunnel," Proc. Inst. Civ. Engrs., 
Vol. LXXX, p. 382, 1885, 4 pages. Concise description of 
this tunnel, the method of driving, ventilation, and costs. 

Trevellini, Luigi, " The Carrito Cocullo Tunnel," Proc. Inst. 
Civ. Engrs., Vol. LXXXII, p. 412, 1885. Description of 
the tunnel followed by the rates of driving Mt. Cenis, St. 
Gothard, Arlberg, Laveno, and Carrito tunnels. 

W. H. E., "The Longest Tunnel in the World," Proc. Inst. Civ. 
Engrs., Vol. LXXXVII, p. 496, 1886. A short description 
of the mining tunnel at Schemnitz, in Hungary, which was 
completed in 1878 and has a length of 10.27 miles. Cost of 
tunnel, $4,860,000. 

Anon., "A Long Tunnel Completed," Min. Sci. Press, Vol. LII, 
pp. 273-276, 4 cols., illus., Apr. 24, 1886. Describes the work 
at the Big Bend tunnel which was driven to divert the 

360 



i 



BIBLIOGRAPHY 361 

waters of the Feather River and make it possible to secure 
the placer gold on the river bed at Big Bend. 

Searles, W. H., "The Westpoint Tunnel," Proc. Inst. Civ. Engrs., 
Vol. XCVI, p. 414, 1889. Description of the tunnel, method 
of construction, cave, and method of recovery. 

EspiNOSA, Luis, ''Tequiquiac Tunnel," Proc. Inst. Civ. Engrs., 
Vol. CXXVI, p. 426, 1896. Description of a tunnel 5.9 
miles long to drain the valley in which the City of Mexico 
is situated. 

Hay, David H., and Maurice Fitzmaurice, ''The Blackwell 
Tunnel," Proc. Inst. Civ. Engrs., Vol. CXXX, p. 50, 1897, 
48 pages. Full description of this tunnel, together with a 
discussion by the members of the institution. 

Clauss, H., ''The Simplon Tunnel," Proc. Inst. Civ. Engrs., Vol. 
CXXXVII, p. 474, 1899. Condensed description of the 
tunnel, giving grades, lengths, etc. 

House, F. E., "North Bessemer Tunnel," Proc. Eng. Soc, West 
Pa., Vol. XV, p. 238, June, 1899, 12 pages, 4 illus. Near 
Carnegie Steel Works at Bessemer, Pa. Tunnel is 2,900 feet 
long, 21.5 high in center of arch, and 26 wide. Av. speed, 
four feet per day. Air operated shovels for bench. 

Anon., "The Simplon Tunnel," Cassiers, Vol. XVH, p. 179, 
Jan., 1900, 12 pages, illustrated with photos. More or less 
popular account of this tunnel. 

Body, John B., "The Draining of the Valley of Mexico," Proc. 
Inst. Civ. Engrs., Vol. CXLIII, p. 286, 1901, 8 pages. De- 
scription of the valley and review of attempts to drain it. 
Gives full particulars of the work on the approaches to the 
tunnel, together with a short description of the tunnel itself. 

Rogers, A. E., "The Location and Construction of Railway 
Tunnels with particulars of some recent work," Proc. Inst. 
Civ. Engrs., Vol. CXLVI, p. 191, 1901, 10 pages. Treats 
principally of English practice and covers the field indicated 
by the title. 

Hough, Ulysses B., "The Kellogg Tunnel," Min. and Min., 
p. 122, Oct., 1901. Describes the methods used in driving 
this tunnel in Idaho. 



362 MODERN TUNNELING 

Clapp, a. W., "The Aspen Tunnel," E. M. J,, Vol. LXXIII, 
p. 519, Apr. 12, 1902, 3>^ columns. Describes some of the 
difficulties in the U. P. R. R. tunnel, Wyoming. Use of 
steam shovel noted. 

Bain, H. F., *' Driving the Newhouse Tunnel," E. M. /., p. 552, 
Apr. 19, 1902, 6 columns, illustrated. Describes the methods, 
equipment, and costs of this work. 

Wilson, W. B., ''The Cripple Creek Drainage Tunnel," Min. 
Sci. Press, Vol. LXXXVI, p. 36, 3 cols., p. 336, i col., and 
Vol. LXXXVII, p. 130, % cols. . Describes the El Paso 
Drain Tunnel. 

HoBLER, George A., ''Tunnels on the Cairns Railway, Queens- 
land, Australia," Proc. Inst. Civ. Engrs., Vol. CLII, p. 221, 
1903. Portion of a paper on the construction of the moun.- 
tain portion of this railway. Gives methods of driving, an 
illustrated description of timbering, etc. 

Anon., "The Simplon Tunnel," Min. and Min., Vol. XX, p. 390, 
J/2 col. Note concerning the use of parallel headings in 
this tunnel and the use of the Brandt hydraulic drill. 

Anon., "Katterat and Nordal Tunnels, on the Ofot Railway, 
Sweden," Proc. Inst. Civ. Engrs.; Vol. CLVI, p. 450, 1904. 
Description of the . hydro-electric power plant, air mains, 
drills, methods of driving, etc. 

Anon., "The Drainage Tunnel in Mining," Min. Sci. Press, Vol. 
LXXXIX, p. 203, Sept. 24, 1904, I col. editorial. Dis- 
cusses the drainage of 'mines by tunnels and mentions sev- 
eral examples. 

Trench, E. F. C, "Alfreton Second Tunnel," Proc. Inst. Civ, 
Engrs., Vol. CLXI, p. 116, 1905, 9 pages. Descriptions of 
methods of driving, drainage, ventilation, etc. 

Brunton, D. W., "Drainage of the Cripple Creek District," 
E. M. J., Vol. LXXX, p. 818, 12 cols. Report of the Con- 
sulting Engineer as to the feasibility of the project and the 
methods to be employed. 

Anon., "Simplon Tunnel," Min. Sci. Press, Vol. XCI, p. 399, 
Dec. 9, 1905, 2 cols. 

Ripley, G. C, and others, "The Newhouse Tunnel," Min. and 



BIBLIOGRAPHY 363 

Min., Vol. XXVII, p. ^,6, Aug., 1906, 5 cols., p. 72, 5>^ cols. 
Describes the equipment and discusses the methods employed 
and the cost of driving. 

Herrick, R. L., ''The Joker Drainage Tunnel," Min. and Min.y 
Vol. XXVII, p. 470, 1906, 8>^ cols., 6 illus. Description of 
methods and equipment. 

Haupt, L. M., ''Great Tunnels," Cassiers, p. 175, Dec, 1906, 
3 cols. Mentions several great tunnels both in this country 
and abroad. 

HiLDAGE, H. T., "Mining Operations in New York and Vicin- 
ity," Trans. A. L M. £., Vol. XXXVIII, p. 360, 1907, 
37 pages. A very complete description of the tunnels in 
the neighborhood of New York City, with methods of 
driving them. 

Pressel, Dr. K., "Works of the Simplon Tunnel," Proc. Inst. 
Civ. Engrs., Vol. CLXVII, p. 411, 1907. A short review of 
a number of articles published in the Swiss scientific papers, 
bringing the history of the undertaking down to the open- 
ing of the tunnel for traffic. 

Fox, Francis, "The Simplon Tunnel," Proc. Inst. Civ. Engrs., 
Vol. CLXXV, p. 61, 1907, 50 pages, illus. A most complete 
and comprehensive description of the tunnel, methods of 
driving, plans adopted to overcome the difficulties encoun- 
tered, costs, etc. 

DiNSMORE, W. P. J., "Western Practice in Tunnel Driving," 
Mine and Quarry, p. 118, May, 1907, 5 pages, illus. Describes 
the equipment and methods used in driving the Ophelia 
tunnel. Cripple Creek, Col. 

Anon., "The Commercial Aspects of Present and Proposed 
Alpine R. R. Tunnels," Editorial, Eng. News, p. 613, Dec. 5, 
1907, 3 pages, with excellent map, showing sixteen tunnels 
in the Alps. 

CoMSTOCK, Chas. W., "Great Tunnels of the World," Colo. Set. 
Soc., Vol. VIII, p. 363-386, Dec. 7, 1907. Discusses tem- 
perature and pressure in deep tunnels. Describes the Mt. 
Cenis, the Hoosac, the St. Gothard, and the Simplon 
tunnels. 



364 MODERN TUNNELING 

Anon., ''Preliminary Work on the Los Angeles Aqueduct," Eng, 
Rec, p. 144, Feb. 8, 1908, 3^ pages, illus. Describes scheme 
of aqueduct and work done up to Jan. i, 1908. Describes 
power plants for supplying aqueduct. Describes equipment 
for Elizabeth tunnel. 

Anon., "The Second Raton Hill Tunnel of the A. T. and Santa 
Fe Railway," Eng. Rec, p. 461, Apr. 4, 1908, 7 cols, illus. 
Describes the methods and equipment used in this work. 

Anon., "A Private Sewer in Rock Excavation," Eng. Rec, 
p. 496, Apr. II, 1908, 8 cols., illus. Describes construction of 
a six-foot sewer draining submerged yards of the new Grand 
Central station. New York. 

Ridge WAY, Robt., "Sub-surface Investigations on the Catskill 
Aqueduct," Eng. Rec, p. 522, Apr. 18, 1908, 8 cols., illus., 
and Eng. Rec, p. 557, Apr. 25, 1908, 8 cols., illus. Describes 
preliminary explorative investigations. Abstract of a paper 
before municipal engineers. New York City. 

DiNSMORE, W. P. J., "The Second Raton Hill Tunnel of the 
Atchison, Topeka and Santa Fe Railway," Mine and Quarry, 
p. 225, June, 1908, 10 cols., 5 illus. Describes the methods 
and equipment used in this work. 

BuNCE, Walter H., "Tunnel Driving at Low Cost," Min. Set. 
Press, p. 60, July 11, 1908. Discusses the equipment, meth- 
ods, and costs of driving the Chipeta Adit at Ouray, Col. 

DiNSMORE, W. P. J., "Western Practice in Tunnel Driving," 
Min. and Met. Journal, Aug. 7, 1908, 3 pages, illus. Plan of 
work, arrangement of holes, handling of waste rock, and 
other important points in the driving of the OpheHa Tunnel 
in the Cripple Creek district. Col. 

Aims, Walter L, "Methods Employed in Driving Alpine Tun- 
nels, The Loetschberg," Eng. News, p. 746, Dec. 31, 1908, 
and also Comp. Air Mag., p. 5163, Feb., 1909. Description 
of methods and equipment. 

Anon., "Harvesting Tunnel, Norwegian State Railways," Proc 
Inst. Civ. Engrs., Vol. CLXXVI, p. 353, 1909. Short de- 
scription giving length, cost, time required to drive, etc. 

BoNNiN, R., "The Loetschberg Tunnel," Proc Inst. Civ. Engrs., 



BIBLIOGRAPHY 365 

Vol. CLXXVII, p. 310, 1909. Short description giving 
methods of driving and difficulties encountered in the work. 
Describes the inrush of peaty material which swamped the 
working and drowned twenty-five men. 

Young, Henry A., "Methods of Tunnel Work and Cost Data 
on an Irrigation Project," Eng. News, p. 128, Feb. 4, 1909. 
Concerning three small tunnels in Montana. 

Anon., "The Roosevelt Tunnel," Min. and Min., p. 387, Apr., 
1909, g}4 cols., 6 illus. Describes some of the difficulties 
encountered in this work and the methods employed to 
meet them. 

Chadwick, L. R., "Driving the Mauch Chunk Tunnel," Mine 
and Quarry, p. 304, June, 1909, 3 pages, illus. Describes some 
of the methods used in driving this tunnel. 

Anon., "Progress of the Northwest Water Tunnel in Chicago," 
Eng. Rec, p. 144, Aug. 7, 1909. Description of the tunnel 
and the methods used in driving it. 

McCoNNELL, I. W., "The Gunnison Tunnel of the Uncompaghre 
Valley Project, U. S. R. S.," Eng. Rec, p. 228, Aug. 28, 1909, 
15 cols., illus. Describes the methods and equipment em- 
ployed in the construction of this tunnel. 

DiNSMORE, W. P. J., "The Gunnison Tunnel," Mine and Quarry, 
p. 315, Sept., 1909, 6 pages, illus. Describes the work of 
enlarging the heading to full size, and some of the difficulties 
encountered during the progress of the tunnel. 

Heinly, B. a., "The Longest Aqueduct in the World," Outlook, 
Vol. XCIII, pp. 215-220, Sept. 25, 1909. Good non- 
technical account of the Los Angeles aqueduct. 

Bagg, Rufus M., Jr., "Roosevelt Deep Drainage Tunnel, Col.," 
E. M. J., p. 106 1, Nov. 27, 1909, 2 pages, illus. 

Bain, H. F., "Tunnel Driving in Colorado," Min. Sci. 
Press, Dec. 4, 1909, pp. 733-47. Describes the methods 
used in driving the Newhouse, Roosevelt, and Gunnison 
tunnels. 

Anon., "Proposed Delivery System of the Catskill Water Sup- 
ply," Eng. Rec, Dec. 11, 1909, 1,500 words. Plan, profile, 
and description of the system. 



366 MODERN TUNNELING 

McCoNNELL, I. W., '* Gunnison Tunnel, Uncompahgre Valley 
Irrigation System," Proc. Inst. Civ. Engrs., Vol. CLXXIX, 
-p. 381, 1910. A short description of the Gunnison tunnel, 
giving length, size, etc. 

Bagg, Rufus M., "Tunnel Driving in Colorado," Proc. Inst. 
Civ. Engrs., Vol. CLXXX, p. 362, 1910. Description of the 
method of driving the Roosevelt deep drainage tunnel at 
Cripple Creek. 

Jacobs, Chas. M., ''The Hudson River Tunnels on the Hudson 
and Manhattan Railway, Proc. Inst. Civ. Engrs., Vol. 
CLXXXI, p. 169, 1910. A very complete and compre- 
hensive description of these tunnels, followed by a discus- 
sion by the members, covering 88 pages. 

Anon., "The New Buffalo Water Works Tunnel," Proc. Inst. Civ. 
Engrs., Vol. CLXXXH, p. 340, 19 10. Short description of 
the concrete-lined tunnel, 10,845 f^^t long, under Lake Erie. 

WiGGiN, Thos. H., "The Design of Pressure Tunnels of the 
Catskill Aqueduct," Eng. Rec, Jan. 29, 1910. Describing 
deep concrete-lined tunnels which are to be subjected to 
hydrostatic pressure. 

Anon., "Walkill Pressure Tunnel," Eng. Rec, p. 45c, Apr. 2, 
1910. Describes the preliminary investigations and the 
equipment installed for this work. 

Anon., "The Hunters Brook Tunnel Construction," Eng. Rec, 
p. 454, Apr. 2, 1 910. Describes the equipment and methods 
employed in this work. 

Anon., "Tunnels in Being and Tunnels to Come," Sci. Amer., 
Apr. 23, 1910, 1,200 words. Discusses length, elevation, 
cost, etc., of famous mountain tunnels. 

Hancock, H. S., Jr., "Method and Cost of Constructing a 
Water-Supply Tunnel Through Rock by Day Labor, and 
Costs of Supplementary Structures," Engng. Contng., May 
25, 191 o, 6>3 pages, illus. Discusses the choice of power 
and describes the equipment and methods used in driving 
a water-supply tunnel for Fort WiUiams, Ont. 

Anon., "Report on the Proposed Board of Water-Supply Pressure 
Tunnel beneath New York City," Eng. News, p. 655, June 2, 



BIBLIOGRAPHY 367 

1910, 4,000 words. Brief historical account of the project, 
with presentation of estimates and discussion of this and 
other distribution plans. 

Lavis, F., ''The New Buffalo Water Works Tunnel," Eng. Rec, 
p. 802, June 25, 1910. Description of methods of driving 
and lining a hard-rock tunnel under compressed air. 

Anon., " Laramie-Poudre Tunnel," Ettg. Rec, p. n, July 2, 19 10, 
3 cols., illus. Description of work on Laramie tunnel. 

Herrick, R. L., "Tunneling on the Los Angeles Aqueduct," 
Min. and Min., p. no, Oct., 1910, approx. 8 pages. Re- 
printed in Leyner Bull., 1026. Describes the methods used 
and gives figures showing the cost of the work. 

Dodge, S. D., and Wm. B. Hake, "The Hudson River Siphon 
Crossing of the Catskill Aqueduct," Eng. Rec, p. 414, Oct. 
8, 1910, and p. 435, Oct. 15, 1910. Abstract given before 
mining engineers. New York, describing preliminary investi- 
gations and sinking of shafts. 

HuLSART, C. Raymond, "Excavation of the Walkill Pressure 
Tunnel," Eng. News, p. 406, Oct. 20, 1910, 15 cols., 10 illus. 
Describes the methods and equipment used in driving this 
tunnel. 

Anon., "Driving Spiral Tunnels on the Can. Pac. Ry.," Eng. 
News, p. 512, Nov. 10, 1910, and also Comp. Air Mag., 
p. 5931, Feb., 191 1, 6X cols., 5 illus. Illustrated descrip- 
tion of this work. 

Palmer, Leroy A., "Utah Metals Company Tunnel," Mines and 
Minerals, p. 296, Dec, 1910, 3 cols., illus. Description of 
methods and equipment for driving tunnel which is intended 
for transportation of ores from Bingham to smelter at Tooele. 

G. H. S., "Tunnels of Switzerland," Proc Inst. Civ. Engrs., Vol. 
CLXXXIV, p. 369, 191 1. List of the 415 tunnels in Swit- 
zerland, giving their length and elevation. 

WiLGUs, Wm. John, "The Detroit River Tunnel," Proc. Inst. 
Civ. Engrs., Vol. CLXXXV, p. 2, 191 1. Comprehensive and 
complete description of the Detroit River tunnel, followed by 
a discussion of this paper by the members present. 

Coy, B. G., "The Laramie-Poudre Tunnel," Eng. Rec, Jan, 14, 



368 MODERN TUNNELING 

191 1. Reprinted in Leyner Bulletin 1029. Description of 
methods used in driving this tunnel. 

Lytel, J. L., "The Strawberry Tunnel, U. S. R. S./' Eng. Rec, 
p. 433, Apr. 22, 191 1, 8 cols., illus. Describes methods, 
equipment, and cost of driving this tunnel. 

Doll, M. G., ''Strawberry Valley Tunnel of the Strawberry Val- 
ley Irrigation Project of Utah," Mine and Quarry, p. 483, 
May, 191 1, II pages, illus. Describes the methods and 
equipment and gives some figures showing the cost of this 
work. 

Anon., ''Joining the Headings of the Loetschberg Tunnel," Eng. 
Rec, p. 491, May 6, 191 1. Contains a brief discussion of 
the methods used in driving this tunnel. 

Flynn, Alfred D., "Rondout Pressure Tunnel of the Catskill 
Aqueduct," Eng. News, p. 654, June i, 191 1, 7 pages, pro- 
fusely illustrated. Describes the tunnel chiefly from the 
point of view of design. 

Zalinski, Ed. R., "Driving the Strawberry Tunnel," E. M. /., 
p. 1 1 53, June 10, 191 1, 2 pages, illus. A description of the 
equipment and routine adopted by the U. S. R. S. in driving 
a four-mile concrete-lined tunnel for irrigation water for 
Utah Valley. 

Hardesty, W. p., "CorneKus Gap Tunnel, United Rys. Co., 
near Portland, Oregon," Eng. News, p. 783, June 29, 1911, 
2 cols, illus. Brief description of the methods and equipment. 

Saunders, W. L., "Tunnel Driving in the Alps," Bull. Am. Inst. 
Min. Engrs., No. 55, p. 507, July, 191 1, 32 pages, illus. 
Describes and discusses the methods and equipment em- 
ployed in driving the Simplon and the Loetschberg Tunnels. 

Anon., "Newton Pressure Tunnel of the Metropohtan Water 

Works, Boston," Eng. Rec, Oct. 28, 191 1. Description of 

•a concrete-lined water-way in rock, with short section of 

80-inch, mortar-lined and concrete-covered steel pipe at 

each end. 

Anon., "Work in the Snake Creek Tunnel," Min. Sci. Press, 
p. 108, Jan. 13, 191 2. A brief description of some of the 
methods used in this work. 



BIBLIOGRAPHY 369 

Anon., *' Notes in Driving the Elizabeth Lake Tunnel," Eng. Rec, 
p. 72, Jan. 20, 191 2, 2 cols. An abstract from the annual 
report of the chief engineer of Los Angeles aqueduct for the 
year ending June 30, 191 1, describing several interesting 
features of the work. 

Anon., "A Tunnel Street," Municipal Journal, p. 199, Feb. 8, 
191 2, 4 cols., illus. Proposed tunnel in upper part of New 
York City to provide access to subway. Concrete lining. 
Provision for removing seepage water. White cement finish. 
Electric Hghting. Unit contract prices. 

Coy, Burgis G., ''The Laramie-Poudre Tunnel," Proceedings of 
Amer. Soc. of Civ. Engrs., p. 217, March, 1912, 14 pages, 13 
illus. Description of the equipment and methods of driving, 

Brunton, D. W., "Notes on the Laramie Tunnel," Bui. No. 64, 
Amer. Inst. Min. Engrs., p. 357, Apr., 191 2, and also abstract 
in Engng. and Min. Wld., p. 959, May 4, 191 2. Describes 
the equipment and methods used at this tunnel. 

Gavin, W. H., "Arthur's Pass Tunnel," Eng. News, p. 870, 
May 9, 191 2. A description of a five-mile railway tunnel in 
New Zealand. 

Russell, Will C, "Driving a Long Adit at Bonanza, Col.," 
Eng. and Min. Jour., p. 272, Feb. i, 1913. An adit, 7 x 8 ft. 
in the clear, was driven 6,235 feet, for drainage, exploration, 
and working, at a cost of $19.87 per foot. Two machines 
on cross-bars were used. The adit was completed in seven- 
teen months and two days. 

WATER-POWER 

Gray, J. W., "Useful Hydraulic Data," Min. Sci. Press, Vol. 
LXXVI, p. 179, 1897, 4K cols. Abstract of a paper in New 
Zealand Mines report by Alex. Aitken, Mgr. Govt. Water, 
Kumara, New Zealand. Power of water. Friction in pipes 
and channels, carrying capacity of pipes and channels, 
capacity of sluices. 

WooDBRiDGE, D. E., "The Hydraulic Compressed Air Power 
Plant at the Victoria Mine (Mich.),"£.ilf./.,p. 125, Jan. 19, 



370 MODERN TUNNELING 

1907. An illustrated article describing an installation of 
the Taylor system. The tested efficiency of this plant is 
given as 82 per cent. 

Edit., ''The Utilization of Small Water Powers," Editorial, Eng. 
Rec, p. 247, Sept. 7, 1907. Discusses the development of 
comparatively small streams. 

Anon., ''Efficiency of Hydraulic Air Compression," E. M. /., 
p. 228, Aug. I, 1908, 3 cols., illus. Abstract of article in 
Gluckauf for March 14, 1908, by O. Bernstein. Contains a 
description of a hydraulic compressor installed in one of 
the mines at Clausthal, together with tests of its efficiency. 

Stewart, Sylvester, "Water Power from Streams of Moderate 
Fall," Cassier^s Mag., p. 470, Sept., 1909, 9 cols., 8 illus. Dis- 
cusses the possibilities for power development with low 
dams. 

McFarlane, Geo. C, "Compressing Air by Water," Min. Sci. 
Press, p. 281, Feb. 19, 19 10, 2 cols., illus. Discusses ways of 
using water-power which is so often available in mining 
districts for the compression of air, and describes several 
devices for doing this. 

KoESTER, Frank, "A General Review of the Hydro-electric 
Engineering Practice," Engr. Mag., 5 articles: Introduc- 
tion, Dams, p. 24, April, 1910; Head Races, Pressure Pipes, 
Penstocks, p. 176, May, 1910; Turbines and Mechanical 
Equipment of Power Plant, p. 340, June, 19 10; Electrical 
Equipment, p. 494, July, 1910; High Tension Transmission, 
p. 659, Aug., 1910. 

Anon., "Taylor Hydraulic Air Compressor (Cobalt)," Comp. Air 
Mag., p. 5675, June, 1910, 6]A cols. Description taken from 
an article in Mines and Minerals, by C. H. Taylor. 

Gray, Alex., "Power Plants of the Cobalt District, Ontario," 
The Min. World, p. 131, July 23, 1910, 11^ cols., 10 illus. 

CoY, B. G., "The Laramie-Poudre Tunnel," Eng. Rec, Jan. 14, 
1911,4 cols., illus. Contains a description of the water-power 
plant used in driving this tunnel. 

VON ScHON, H., "The Most Resourceful UtiHzation of Water 
Power," Eng. Mag., p. 69, April, 191 1, 21 cols., 5 illus. 



^ 



BIBLIOGRAPHY 371 

Bateman, G. C, ''Cobalt Hydraulic Company," E. M. /., p. 998, 

Nov. 18, 191 1, 1,000 words. Description of a Taylor 

. compressor in which the air is drawn into a faUing column 

of water. Compressed air is sold at 25 cents per 1,000 cu. ft. 

at 120 lbs. pressure. 

Coy, B. G., ''The Laramie-Poudre Tunnel," Proc. Am. Soc. Civ. 
Engrs., p. 217, March, 191 2. Contains a description of the 
water-power plant at this tunnel. 

Smith, Cecil B., "Power Plants for Mines in the Cobalt Dis- 
trict," Min. and Eng. World, p. 503, March 2, 191 2, 3^ cols., 
2 illus. Description of water-power plants furnishing power 
to the Cobalt camp. 

Brunton, D. W., "Notes on the Laramie-Poudre Tunnel," 
Trans. Am. Inst. Min. Engrs., p. 357, April, 191 2, also 
abstract in Min. and Engng. World, p. 959, May 5, 191 2. 
Contains a description of the water-power plant at this 
tunnel. 

STEAM POWER 

Webber, Wm. O., "Comparative Costs of Gasoline, Gas, Steam, 
and Electricity for Small Powers," Eng. News, p. 159, Aug. 
15, 1907, 2}4 cols., tables. Gives itemized cost tables for 
2, 6, 10, and 20 horse-power plants. 

Anon., "The Second Raton Hill Tunnel of the Atchison, Topeka 
and Santa Fe Ry.," Eng. Rec, p. 461, April 4, 1908. Con- 
tains a description of the steam-power plant for this tunnel. 

Anon., "Steam vs. Compressed Air in Mining (Coal)," Comp. Air 
Mag., p. 5174, Feb., 1909, i col. Compressed air is much 
better than steam for pumping, coal cutting, etc., in mines. 

Anon., "The Compressed Air Plant for the Rondout Siphon," 
Eng. Rec, p. 490, April 10, 1909, 4^ cols., illus., also Comp. 
Air Mag. (reprint), p. 5291, June, 1909, 7 cols., illus. 

Anon., " Compressed Air in Construction Work," Eng. Rec, p. 179, 
Aug. 14, 1909, 4 cols. Discusses the advantages of com- 
pressed air over steam for the operation of drills, pumps, 
etc., in construction work. 

McCoNNELL, I. W., "The Gunnison Tunnel of the Uncompaghre 



372 MODERN TUNNELING 

Valley Project, U. S. R. S.," Eng. Rec, p. 228, Aug. 28, 1909, 
15 cols., illus. Contains a description of the steam-power 
plants used in this work. 

Chance, T. M., ''Costs of a Gas Engine and of a Combined 
Steam Plant," Eng. Rec, p. 273, Sept. 4, 1909, 7 cols., 4 illus. 
Power economy of gas engine is greater than steam, but its 
first cost and difficulty of operation are also greater. A- 
corresponding plant using low-pressure turbines and high- 
economy Corliss engines solves the problem in many places. 

Anon., "Cost of Power for Various Industries," Eng. Rec, p. 711, 
Dec. 25, 1909. Review of paper before the Boston Society 
of Civil Engineers, by Chas. T. Main. Concerns steam 
power for textile mills, under varying conditions, assuming 
that it is ultimately converted into electricity. 

Webb, Rich. L., "Cost of Producing Compressed Air at a Cana- 
dian Mining Camp," Can. Min. Jour., p. 102, Feb. 15, 1910, 
20 cols., 10 tables. Results of tests on two steam-driven air 
compressors. 

Haight, H. v., "Steam Driven Air Compressors in Cobalt," 
Can. Min. Jour., p. 209, April i, 19 10, 3^/^ cols. Discussion 
of the paper by Rich. L. Webb, Can. Min. Jour., Feb. 15, 
1910, p. 102. 

Anon., "The Hunters Brook Tunnel Construction," Eng. Rec, 
p. 454, April 2, 1 9 10. Contains a description of the steam- 
power plant for this tunnel. 

Anon., " Cost of Power Production in Small Steam Plants," Eng. 
Rec, p. 570, April 30, 19 10. Discusses the cost of steam- 
electric power in small stations. 

Anon., "The Moodna Pressure Tunnel of the Catskill Aqueduct 
(Power Plant)," Eng. Rec, p. 731, June 4, 1910. Descrip- 
tion of the two power plants used to furnish the compressed 
air used in driving this tunnel. 

Anon., "Driving Spiral Tunnels on the Can. Pac. Ry.," Eng. 
News, p. 512, Nov. 10, 1910, 6 cols., 5 illus. Contains a de- 
scription of the steam-power plant for this work. 

Anon., "Exhaust Steam Turbines at Mines," Min. and Min., 
p. 371, Jan., 1912, 5 pages, illus. Abstract of a paper before 



BIBLIOGRAPHY 373 

Australasian Inst. Min. Engrs., June, 191 1. Describes use 
of turbine engines to utilize exhaust steam from various 
engines of a mine plant. 
Clark, S. M., ''The Fuel Cost of Making Steam," The Isolated 
Plant, p. 129, April, 191 2, 12 cols., 3 illus. Discusses the 
means of judging and comparing coal. 

INTERNAL-COMBUSTION POWER 

Webber, Wm. 0., ''Comparative Costs of Gasoline, Gas, Steam, 
and Electricity for Small Powers," Eng. News, p. 159, Aug. 
15, 1907, 2}4 cols., tables. Gives itemized cost tables for 2, 
6, 10, and 20 horse-power plants. 

Thwaite, B. H., "The Blast Furnace as a Center of Power Pro- 
duction," Cassier's Mag., p. 23, Nov., 1903, 36 cols., 15 illus. 

Adams, E. T., "The Development of the Large Gas Engine in 
America," Gassier' s Mag., p. 41, Nov., 1907, 22 cols., 15 illus. 
Development of gas engine supplied with gas from blast 
furnace. 

Humphrey, H. A., "By-product Recovery Gas-producer Plants," 
Gassier' s Mag., p. 55, Nov., 1907, 17 cols., 11 illus. Mr. 
Humphrey treats of the recovery of such a valuable com- 
mercial article as sulphate of ammonia from the waste of 
the gas-producer, showing the success which has been 
attained by Dr. Ludwig Mond and his associates. 

Bibbins, J. R., "Recent Applications of Gas Power," Gassier' s 
Mag., p. 147, Nov., 1907, 13 cols., 9 illus. Discusses the 
recent installations of producer-gas plants in this country, 
showing the amount of power so used and the sizes of the 
plants. 

Rowan, F. J., "The Suction Gas Producers," Cassier's Mag., 
p. 174, Nov., 1907, 48K cols., 24 illus. 

Harvey, Elbert A., "Power Gas from Bituminous Coal," Gas- 
sier's Mag., p. 199, Nov., 1907, 14 cols., 8 illus. States that 
the bituminous gas-producer is no longer an experiment, 
and describes several such producers which will give satis- 
factory service. 

RoBSON- Philip W., "Power Gas-producers, their Design and 



374 MODERN TUNNELING 

Application," published by Edward Arnold, London, Eng., 
1908, 247 pages, 105 illus. 

FernalD; R. H., ''Producer-gas Power Plant in the United 
States," Cassier's Mag., p. 582, Feb., 1908, 13 cols. 

Anon., "Test of a Small Gas-producer Plant," Eng. Rec, p. 375, 
March 28, 1908, 2^ cols. Describes the 15 horse-power 
plant of the Weber Wagon Works, Chicago, and gives the 
results of tests. 

Barbezat, Alfred, "Recent Developments in the Gas Turbine," 
Gassier^ s Mag., p. 617, April, 1908, 6 cols., 3 illus. 

Anon., "The Loomis-Pettibone Gas-generating System," Cas- 
sier^s Mag., p. 685, April, 1908, 2 cols. A discussion of the 
principles underlying this system for use with bituminous coal. 

Anon., "A Producer-gas Power Plant," Eng. Rec, p. 478, April 4, 
1908. A brief reference to a test of a 600 horse-power pro- 
ducer-gas plant at the works of David Rowan & Co., at 
Glasgow. 

Lewis, W. Y., "The Carbon Monoxide Gas-producer," Gassier^ s 
Mag., p. 223, July, 1908, id>}4 cols. Discusses the advan- 
tages of a straight carbon monoxide gas-producer as devel- 
oped at the Phoenix Tube Mill plant in Long Island City. 

Anon., "The Suction Gas-producer Plant at the Shops of Fair- 
banks, Morse & Co.," Eng. Rec, Sept. 5, 1908. Description 
of this plant, giving also results of tests. 

White, T. L., "The Reliabihty of the Gas-producer Plant," 
Gassier^ s Mag., Oct., 1908, $% pages. Describes a test made 
upon a small gas-producer plant, and discusses gas plants 
from a point of view of reliabihty as compared with other 
plants. 

Burt, T. W., "The Suction Gas-producer," Gassier^ s Mag., 
p. 124, June, 1909, II pages. Description of the theory and 
design of the suction gas-producer with drawings of four 
important types. 

Anon., "Test of a Double Zone Bituminous Gas-producer," Eng. 
News, p. 13, July i, 1909, 7 cols., 4 illus. Results of experi- 
mental work at the plant of the Westinghouse Machine Co., 
at East Pittsburgh. 



BIBLIOGRAPHY 375 

Atkinson, A. S., ^'Gas Engines for Mining Purposes," Min. 
Set. Press, p. 300, Aug. 28, 1909, 3^^+ cols. Discusses the 
advantages of gas engines for mining power plants, showing 
some of their advantages over steam and electricity. 

Chance, T. M., ''Costs of a Steam Engine and of a Combined 
Steam Plant," Eng. Rec, p. 273, Sept. 4, 1909, 7 cols., 4 illus. 
Power economy of gas engine is greater than steam, but its 
first cost and difficulty of operation are also greater. A cor- 
responding plant using low-pressure turbines and high- 
economy Corliss engines solves the problem in many places. 

Gradenwitz, Dr. Alfred, ''A New Gas-producer for Low, 
Grade Fuel," Power and the Engineer^ p. 653, Oct. 19, 1909, 
3^^ cols., 3 illus. Discusses a gas-producer designed to oper- 
ate upon anthracite, coke, and smoke-chamber dust and 
other rubbish, giving figures showing the consumption of 
these materials per horse-power hour. 

SuPLEE, Henry H., ''The Explosion Gas Turbine," Gassier^ s 
Mag., p. 79, Nov., 1909, 6 cols., 2 illus. Describes an experi- 
mental explosion gas turbine of 2 horse-power as developed 
by M. Karavodine in Paris. 

Anon., "Tests of a Suction Gas-producer," Univ. of 111. Bull. 50, 
90 pages, illus. and tables. Reviews theory of gas-producer, 
explaining object of tests, methods of experimenting, giving 
results and conclusions. 

Fernald, R. H., "Features of Producer-gas Power-plant Devel- 
opment in Europe," (U. S.) Bureau of Mines Bulletin 4, 1910, 
27 pages, 4 plates, 7 figs. Briefly summarizes some features 
of gas-producer practice with particular reference to the use 
of low-grade fuels. 

Miller, J. C, "Power Gas and Gas-producer," published by 
Popular Mechanics Co., Chicago, 111., 1910, 184 pages. 

Clement, J. K., L. H. Adams, and C. N. Haskins, "Essential 
Factors in the Formation of Producer-gas," (U. S.) Bureau 
of Mines, Bulletin 7, 191 1, 58 pages, i plate, 16 figs. De- 
scribes laboratory experiments bearing on the rate of forma- 
tion of carbon monoxide at high temperatures and the 
effect of temperature on the rate of formation and the 



376 MODERN TUNNELING 

composition of water gas. Indicates how the results of the 
tests apply to the operation of boiler furnaces and gas- 
producers. 

Fernald, R. H., and CD. Smith, ''Resume of Producer-gas 
Investigations," Oct. i, 1904, to June 30, 19 10, (U. S.) 
Bureau of Mines, Bulletin ij, 191 1, 393 pages, 12 plates, 250 
figs. Summarizes the results of producer-gas investigations 
at the Government fuel- testing plants. Incidentally dis- 
cusses gas-producer development in this country and in 
Europe. Is intended especially for mechanical engineers 
and power-plant officials interested in gas-producer design 
and in the operation of gas-producers on the coals available 
at different points in the United States. 

Davis, C. A., "The Uses of Peat for Fuel and Other Purposes," 
(U. S.) Bureau of Mines, Bulletin 16, 191 1, 214 pages, i plate, 
I fig. Summarizes recent developments in the utilization 
of peat. Treats pf the origin and formation of peat, its fuel 
value, and the manufacture of peat fuel. Also summarizes 
progress in utilizing peat for other purposes. 

Smith, C. D., J. K. Clement, and H. A. Grine, ''Incidental 
Problems in Gas-producer Tests," (U. S.) Bureau of Mines, 
Bulletin Ji, 29 pages, 8 figs. Considers the factors affecting 
the proper length of gas-producer tests and the differences 
in temperatures at different points in the fuel bed. Reprint 
of the (U. S.) Geol. Survey Bulletin jpj. 

Strong, R. M., "Commercial Deductions from Comparisons of 
Gasoline and Alcohol Tests of Internal-combustion Engines," 
(U. S.) Bureau of Mines, Bulletin J2, ^S pages. Summarizes 
deductions based on 2,000 tests of gasoline and alcohol. 
Reprint of (U. S.) Geol. Survey Bulletin jg2. 

WiTZ, A., "The Use of Gas Engines in Central Stations (L'Em- 
ploi des moteurs a gaz dans les stations centrales d'electri- 
cite)," Genie Civil, No. 28,861 D.,Nov. 11, 191 1, 5,600 words. 
Discussion of the feasibility of the use of gas, and results 
of some of the tests made. 

Meriam, J. B., "The Relative Economy of Gas Engines and 
Other Sources of Power," Jour. Cleveland Engng, Soc., p. 121, 



BIBLIOGRAPHY 377 

Dec, 191 1, 2,200 words, illus. Discusses the advantages and 
disadvantages of oil and gas engines in plants of moderate 
size and gives examples of recent installations. 

Anon., ''New Bituminous Gas-producer," Iron Age, Dec. 14, 
191 1, 1,200 words, illus. Illustrates and describes the Nor- 
densson furnace gas-producer. 

Weil, J. A., ''Producer- gas," Mech. Engr.,p. 755, Dec. 15, 1911, 
3,000 words. Discusses the proper design of plant. 

Strong, R. M., and Lauson Stone, "Comparative Fuel Values 
of Gasoline and Denatured Alcohol in Internal- Combustion 
Engines," (U. S.) Bureau of Mines, Bulletin 4j, 191 2, 243 
pages, 3 plates, 32 figs. A detailed statement of the results 
of 2,000 tests made to determine the comparative value of 
the two fuels for use in internal-combustion engines. Is a 
technical report, written for mechanical engineers and per- 
sons interested in the utilization of liquid fuels. 

Fernald, R. H., "The Status of the Gas-producer and the 
Internal-combustion Engine in the Utilization of Fuels," 
(U. S.) Bureau of Mines, Technical Paper g, 191 2, 42 pages, 
6 figs. Relates the progress in the application of the gas- 
producer to commercial uses, and in the development of 
gas power. 

Anon., "An English Wood Refuse Suction Gas-producer," Sci. 
Amer., p. 3, Supplement No. 1879, Jan. 6, 191 2, i col. 
Describes the machine and discusses its advantages. 

Anon., "Temporary Power Plant for the Woolwich Footway 
Tunnel," Engineer (London), p. 46, Jan. 12, 191 2, 2 pages, 
illus. Description of a plant using suction gas-producers as 
a source of motive power to operate the air-compressors for 
a tunnel under the Thames driven under compressed 
air. 

Anon., "The Gas Power Field for 191 1, a Review of the 
Past Year," Sci. Amer., p. 58, Supplement No. 1,882, Jan. 
27, 191 2, 6 cols. Paper read before the Gas Power Section 
of the American Association of Mechanical Engineers. 

Anon., "The Bituminous Gas Engine in South Africa," The En- 
gineer, p. 258, March 8, 191 2, 4 cols., 3 photos. Describes 



378 MODERN TUNNELING 

the producer and gives results of its use at the Groenfontein 
tin mines in the Transvaal. 

Percy, Paul C, '' Combination Power and Ice Plant," Power, 
p. 418, March 26, 191 2, 8 illus. Describes a plant using 
wood-refuse gas-producers as prime movers and gives results 
of tests. 

Anon., '' What is the Diesel Engine? " Eng. News, pp. 654-6, 
April 4, 191 2, 6)4 cols. An excellent recitation in non- 
technical language of the principles upon which this machine 
operates. 

Chorlton, Alan E. L., " Gas Engines for Collieries,'' Coal 
Age, pp. 876-9, April 13, 191 2, 5 illus. Gas engines are 
being largely used at British colHeries for the generation 
of power. The gas is generated either in producers or in 
coke ovens. Producers can be sometimes made to yield 
such products from by-products, where the fuel is of low 
grade, that even without using the gas produced, the in- 
stallation will justify its erection. (Paper read before Mid- 
land Institute of Mining, Civil, and Mechanical Engineers.) 

Diesel, Rudolph, " The Present Status of the Diesel Engine 
in Europe," Jour. Am. Soc. Mech. Engrs., June, 191 2, 40 
pages, 50 illus. 

Garland, C. M., '' Bituminous Coal Producers for Vower/Uour. 
Am. Soc. Mech. Engrs., p. 833, June, 191 2, 20 pages, 2 
illus. Describes the apparatus and general arrangement 
of bituminous-coal producers as designed for power. Dis- 
cusses also the efficiency of the plant, composition of the 
gas, and operating costs. 

ELECTRIC POWER 

ScHAEFER, E. F., '' Compressed Air vs. Electricity," Min. and 
Min., p. 425, April, 1906, 2}^ cols. Discusses the advantages 
of compressed air over electricity for mining purposes. 

Webber, Wm. 0., '' Comparative Costs of Gasoline, Gas, Steam, 
and Electricity for Small Powers," Eng. News, p. 159, Aug. 
15, 1907, 2>^ cols., tables. Gives itemized cost tables 
for 2, 6, 10, and 20 horse-power plants. 



BIBLIOGRAPHY 379 

Kerr, E. W., ''Power and Power Transmission," 1908, 366 
pages. Published by John Wiley & Sons, New York City. 

, " Electric Power Costs in Small Station," Eng. Rec, p. 

30, Jan. 9, 1909, i^ cols. Discusses the power costs 
at several small towns near Boston, Mass. 

Spellmire, W. p., " The Use of Electricity as Applied to Coal 
Mining," E. M. J., p. 507, March 6, 1909. Discusses the 
advantages of electricity as a source of power for coal- 
mining plants. 

Anon., " Cost of Power for Various Industries," Eng. Rec, p. 711, 
Dec. 25, 1909. Review of paper before the Boston Society 
of Civil Engineers, by Chas. T. Main. Concerns steam 
power for textile mills under varying conditions, assuming 
that it was ultimately converted into electricity. 

KoESTER, Frank, ''A General Review of the Hydro-electric 
Engineering Practice," Engr. Mag., 5 articles: Introduction, 
Dams, p. 24, April, 1910; Head Races, Pressure Pipes, 
Penstocks, p. 176, May, 19 10; Turbines and Mechanical 
Equipment of Power Plant, p. 340, June, 19 10; Electrical 
Equipment, p. 494, July, 19 10; and High Tension Trans- 
mission, p. 659, Aug., 1910. 

Anon., '' Cost of Power Production in Small Steam Plants," £;z^. 
Rec, p. 570, April 30, 1910. Discusses the cost of steam- 
electric power in small stations. 

Anon., '' Cost of Power Transmission, Electricity vs. Compressed 
Air," Min. Set. Press, p. 700, May 14, 1910, }^ col. Esti- 
mates prepared by the Pneumelectric Machine Co., for 
the cost of dehvering 200 horse-power one mile by com- 
pressed air and electricity (direct current, 250 volts). 

Anon., " Methods and Costs of Constructing a Water Supply 
Tunnel," Engng. Contng., p. 472, May 25, 1910, 6 cols., 6 
illus. Describes the electrically driven power plant for 
this work near Ft. Williams, Ont. 

Anon., " Electricity in the Construction of the Los Angeles 
Aqueduct," Eng. Rec, July 16, 1910, 6 cols., illus. De- 
scribes central generating station and cost of trans- 
mission line. 



380 MODERN TUNNELING 

HuLSART, C. R., '' Excavation of the Wallkill Pressure Tunnel, 
Catskill Aqueduct," Eng. News, p. 406, Oct. 20, 1910, 15 
cols., 10 illus. Contains a description of the electrically 
driven power plant for this work. 

Yerbury, H. E., '' Electricity as Applied to Modern Tunnel 
Work," Proc. Inst. Civ. Engrs., Vol. CLXXXIII, p. 296, 
191 1, 8 pages. Discusses the application of electricity to 
tunneling work; giving description of power station, tunnel 
equipment, tunnel driving, etc. 

Edit., " High Tension Line Problems," Editorial Eng. Rec, p. 
289, March 18, 191 1. Discusses some of the difficulties 
connected with high-tension electric lines. 

Knowlton, H. S., " Developing Electrical Energy from the 
Los Angeles Aqueduct," Elec. World, p. 301, Feb. 10, 191 2, 
12 cols., illus. Plans for estabHshing a large hydro-electric 
system in connection with the creation of a new water 
supply. Electrical energy will be sold as a by-product 
of a $23,000,000 water system. Maximum delivery 90,000 
kilowatts into city of Los Angeles. Extensive use of 
electricity in aqueduct construction. 

COMPRESSED AIR POWER 

ScHAEFER, E. F., ''Compressed Air vs. Electricity," Min. and 
Min., p. 425, April, 1906, 2}^ cols. Discusses the advantages 
of compressed air over electricity for mining purposes. 

Gray, Alex., "Compressed Air for Mining in Cobalt District," 
Min. Wld., p. 877, Dec. 12, 1908, 6}^ cols., 2 illus. Factors 
influencing the supply of air for mines. Marked increase 
in steam and gas-producer plants in last four years. Cost 
of compressing air. Taylor hydraulic air-compressor system. 

Anon., ''Steam vs. Compressed Air in Mining" (Coal), Comp. Air 
Mag., p. 5174, Feb., 1909, i col. Compressed air is much 
better than steam for pumping, coal cutting, etc., in mines. 

Anon., ''Compressed Air in Construction Work," Eng. Rec, p. 
179, Aug. 14, 1909, 4 cols. Discusses the advantages of 
compressed air over steam for the operation of drills, 
pumps, etc., in construction work. 



BIBLIOGRAPHY 381 

Anon., "Cost of Power Transmission: Electricity vs. Compressed 
Air," Mi7t. Sci. Press, p. 700, May 14, 1910. Estimates 
prepared by the Pneumelectric Machine Co. for the cost of 
delivering 200 horse-power one mile by compressed air and 
electricity (direct current, 250 V.). 

\'iLLETARD, H., ''AppUcation of Compressed Air in Tunnels 
(Applications de I'air comprime a la perforation des grands 
sou terrains)," Tech. Mod., Nov., 191 1, 2,500 words, illus. 
With particular reference to large European railway tunnels. 

POWER TRANSMISSION 

LucKE, Charles E., "Power Transmission by Producer-gas," 
Gassier' s Mag., p. 210, Nov., 1907, 6 cols. Discusses 
the advantages of producer-gas as a means of power 
transmission. 

Richards, Frank, "Compressed Air Leakage," Comp. Air Mag., 
p. 4717, Jan., 1908, 2^ cols. Examples where pipe did 
not leak. 

Smith, C. A., "Power Transmission," Cassier^s Mag., p. 275, 
July, 1908, io>^ cols. A comparative study of the merits 
of gas and electricity. 

Emerson, Harrison Dexter, "Long-Distance Gas Transmis- 
sion," Cassier's Mag., p. 275, May, 1910, 2 cols., 4 illus. 
Facts connected with the long-distance pumping of natural 
gas through pipe Hnes from the fields of Pennsylvania and 
West Virginia. 

Anon., "Cost of Power Transmission: Electricity vs. Compressed 
Air," Mm. Sci. Press, p. 700, May 14, 1910, H col. Estimates 
prepared by the Pneumelectric Machine Co., for the cost of 
deHvering 200 horse-power one mile by compressed air and 
electricity (direct current, 250 volts). 

Edit., "High Tension Line Problems," Eng. Rec, p. 289, 
March 18, 191 1. Editorial discusses some of the difficulties 
connected with high-tension electric lines. 

Richards, Frank, "Draining Compressed Air," Comp. Air Mag., 
p. 5997, April, 191 1, 4 cols. Abstract of article in Eng. Rec, 
Feb. 18, 1911, p. 203. 



382 MODERN TUNNELING 

Edit., "Freezing up of Compressed Air Lines," Comp. Air Mag., 

p. 6017, April, 191 1, 2 cols. Editorial. 
MacIntire, H., "Power from Compressed Air," Power, Nov. 7, 

1911, 1,550 words; also Comp. Air Mag., p. 6259, Dec, 1911. 

Discusses air transmission in pipe lines and developing 

power from an air system. 
Anon., "Proportion of Air Mains and Branches," E.M.J., 

p. 1027, Nov. 25, 191 1. A table showing diameters 

of branches that can be supplied by mains of certain 

sizes. 
Anon., "Power from Compressed Air," Amer. Mech., Nov. 30, 

191 1, 1,200 words. Considers the transmission of power by 

an air system; the ec'onomy and applications. 

CHOICE OF POWER 

Webber, Wm. 0., "Comparative Costs of Gasoline, Gas, Steam, 
and Electricity for Small Power," Eng. News, p. 159, Aug. 
15, 1907, 2>^ cols., tables. Gives itemized cost tables for 
2, 6, 10, and 20 horse-power plants. 

Moses, Percival R., "Power Plant Waste," Cassier^s Mag., 
p. 497, Oct., 1909, 16 cols.; p. 12, Nov., 1909, 13 cols.; 
p. 320, Feb., 1910, 13 cols. A series of articles dealing with 
waste in power plants and the means of preventing it. 

Anon., "Methods and Costs of Constructing a Water Supply 
Tunnel through Rock," Engng. Contng., p. 472, May 25, 
1910, 6 cols., illus. Discusses the choice of motive power for 
this work near Fort Williams, Ont., electricity being chosen. 

POWER PLANT DESCRIPTIONS 

Anon., "Preliminary Work on the Los Angeles Aqueduct," Eng. 
Rec, p. 144, Feb. 8, 1908. Contains a description of the 
electric power plant for supplying power to the aqueduct 
work. 

Anon., "Test of a Small Gas-producer Plant," Eng. Rec, p. 375, 
March 28, 1908, 2}^ cols. Describes test of 15 horse-power 
plant of the Weber Wagon Works, Chicago, 111. 



BIBLIOGRAPHY 383 

Anon., "The Second Raton Hill Tunnel of the Atchison, Topeka 
and Santa Fe Railway," Eng. Rec, p. 461, April 4, 1908. 
Contains a description of the power plant for this tunnel. 

Anon., ''The Suction Gas-producer Plant at the Shops of Fair- 
banks, Morse & Co.," Eng. Rec, Sept. 5, 1908. Description 
of this plant, giving also results of tests. 

Anon., "The Compressed Air Plant for the Rondout Siphon," 
Eng. Rec, p. 490, April 10, 1909, /^yi cols., illus., and also in 
Comp. Air Mag., p. 5391, June, 1909, 7 cols., illus. Descrip- 
tion of a compressed-air plant of 24,000 cubic feet capacity 
for the Rondout Siphon tunnel of the Catskill Aqueduct. 

McCoNNELL, I. W., "The Gunnison Tunnel of the Uncom- 
paghre Valley Project, U. S. R. S.," Eng. Rec, p. 228, Aug. 
28, 1909, 15 cols., illus. Contains a description of the steam- 
power plants used in this work. 

Atkinson, A. S., "Gas Engines for Mining Purposes," Min. Set. 
Press, p. 300, Aug. 28, 1909. Contains a brief description 
of the gas-engine power plant for the Powell Duffryn 
ColHeries in South Wales. 

Moses, Percival R., "Power Plant Waste," Gassier' s Mag., p. 
497, Oct., 1909, 13 cols. The last of a series of three articles 
deahng with this subject. In this number several specific 
examples are given, showing the defects and preventable 
waste and the remedial methods therefor. 

Anon., "Wallkill Pressure Tunnel," Eng. Rec, p. 450, April 2, 
1 9 10. Contains a description of the power plant installed 
for this work. 

Anon., "The Hunters Brook Tunnel Construction," Eng. Rec, 
p. 454, April 2, 1910. Contains a description of the power 
plant for this tunnel. 

Anon., "Cost of Power Production in Small Steam Plants," p. 
570, Eng. Rec, April 30, 19 10. Discusses the cost of steam- 
electric power in small stations and describes four examples. 

Anon., "Methods and Costs of Constructing a Water Supply 
Tunnel," £w^w^. Contng.,p. 472, May 25, 1910, 6 cols., 6 illus. 
Describes the electrically driven power plant for this work 
near Fort Williams, Ont. 



384 MODERN TUNNELING 

Anon., "The Moodna Pressure Tunnel of the Catskill Aqueduct 
(Power Plants)," Eng. Rec, p. 731, June 4, 19 10. Descrip- 
tion of the two power plants used to furnish the compressed 
air used in driving this tunnel. 

HuLSART, C. R., ''Excavation of the Wallkill Pressure Tunnel, 
Catskill Aqueduct," Eng. News, p. 406, Oct. 20, 1910, 15 
cols., 10 illus. Contains a description of the electrically 
driven power plant for this work. 

Anon., ''Driving Spiral Tunnels on the Canadian Pacific Rail- 
way," Eng. News, p. 512, Nov. 10, 1910, 6 cols., 5 illus. 
Contains a description of the steam-power plant for this 
work. 

Palmer, Leroy A., "Utah Metals Company Tunnel," Min. and 
Min., p. 296, Dec, 1910. Contains a description of the 
water-power plant at this tunnel. 

Coy, B. G., "The Laramie-Poudre Tunnel," Eng. Rec, Jan. 14, 
191 1, 4 cols., illus. Contains a description of the water- 
power plant used in driving this tunnel. 

Lytel, J. L., "The Strawberry Tunnel, U. S. R. S.," Eng. Rec, 
p. 433, April 22, 191 1. Contains a description of the power 
plant for this project. 

Anon., "Temporary Power Plant for Woolwich Footway Tun- 
nel," Engineer (London), p. 46, Jan. 12, 191 2, 2 pages, illus. 
Description of a plant using suction gas-producers as a 
source of motive power to operate the air-compressors for a 
tunnel under the Thames, driven under compressed air. 

Coy, B. G., "The Laramie-Poudre Tunnel," Proc. Am. Soc. Civ. 
Engrs., p. 217, March, 191 2. Contains a description of the 
water-power plant at this tunnel. 

Smith, Cecil B., "Power Plants for the Mines in the Cobalt 
District," Min. and Engr. World, p. 503, March 2, 191 2, 
3^ cols., 2 illus. Description of water-power plants furnish- 
ing power to the Cobalt camp. 

Anon., "The Bituminous Gas Engine in South Africa," The Engi- 
neer, p. 258, March 8, 191 2, 4 cols., 3 photos. Contains a 
description of a bituminous producer plant at the tin mines 
on the Groenfontein farm in the Transvaal. 



BIBLIOGRAPHY 385 

Brunton, D. W., "Notes on the Laramie-Poudre Tunnel/' 
Trans. Am. Inst. Min. Engrs., p. 357, April, 191 2; also 
abstract in Engng. and Min. World, p. 959, May 4, 191 2. 
Contains a description of the water-power plant at this 
tunnel. 

AIR COMPRESSORS 

WiGHTMANjL. I./' Electrically Driven Air Compressors for Metal 
Mining Purposes," Comp. Air Mag., p. 3054, Aug., 1904, 
10^ pages, illus. 

■-, ''The Air Power Plant of the Modern Mine," Min. Mag., 

p. 357, Nov., 1905, 20 cols. Discusses the advantages 
and disadvantages of different types of air compressors. 

, ''Compressed Air, its Production, Transmission, and 

Application," Proc. Eng. Soc. West Penna., Vol. XXII, 
p. 197, June, 1906, 42^2 pages. A detailed discussion of 
the problems encountered in air compression, including 
stage compression, cooling devices, types of compressors, 
and receivers. 

Cone, J. D., "Selection of Proper Air Compressor," Min. and 
Min., Vol. XXVII, p. loi, Oct., 1906, 6K cols., 6 illus. 
Economic and mechanical considerations influencing the 
purchase. 

WooDBRiDGE, D. E., "The Hydraulic Compressed Air Power 
Plant at the Victoria Mine (Mich.)," E. M. /., p. 125, 
Jan. 19, 1907, 5 pages, illus. Description of the Taylor 
system. Tested efficiency, 82 per cent. 

Hart, J. H., "Compressed Air in Mining," E. M. J., Vol. 
LXXXIII, p. 855, 1907, 214 cols., illus. Describes principle 
of the Taylor air compressor and suggests a simple applica- 
tion of it for use in mine shaft. 

Halsey, F. a., "A New Development in Air Compressors," 
E. M. J., Vol. LXXXIV, p. 397, Aug. 31, 1907, 11 cols., illus. 
A constant speed electrically operated, variable delivery air 
compressor that automatically varies the delivery to meet 
fluctuating demand. 

Anon., "Efficiency of Hydraulic Air Compression," E. M. J., 
p. 228, Aug. I, 1908. Abstract of article in GlUckauf, March 



386 MODERN TUNNELING 

14, 1908, by P. Bernstein. Contains a description of a 
hydraulic compressor installed at one of the mines at 
Clausthal, together with tests of its efficiency. 

Brown, C. Vessey, "Air Compressors," Cassier's Mag., p. 511, 
Oct., 1908, 27 pages. Discusses the important features in 
the design of air compressors, and describes a number of 
types and makes. 

Anon., "Rock Excavation with a Portable Air Compressor Out- 
fit," Eng. Rec, p. 25, Jan. 2, 1909, 3 cols., illus. Describes 
and discusses portable gasoline compressor. 

Anon., "High Pressure Gas Transmission," Comp. Air Mag., 
P- 5306, June, 1909, 3 cols. Describes a compressor used 
in pumping the gas for high-pressure transmission. 

Webb, Rich. L., "Cost of Producing Compressed Air at a 
Canadian Mining Camp," Can. Min. Jour., p. 102, Feb. 15, 
1910, 20 cols., 10 tables. Results of tests on two steam- 
driven air compressors. 

McFarlane, Geo. C, " Compressing Air by Water," p. 281, Min. 
Sci. Press, Feb. 19, 1910, 2 cols., illus. Contains descriptions 
of several devices for converting the water-power, which is 
so often available in mining districts, into compressed air. 

Anon., "Taylor Hydraulic Air Compressor (Cobalt)," Comp. 
Air Mag., p. 5675, June, 1910, 6>^ cols. Description taken 
from an article in Mines and Minerals, by C. H. Taylor. 

Rice, Rich. H., "Commercial Application of the Turbo-compres- 
sor," Proc. Am. Soc. Mech. Engrs., p. 303, 191 1, 12 pages, 

6 illus. Describes a turbo-compressor for blast-furnace work 
and its automatic governing mechanism. Gives data upon 
the sizes, capacity, and performance of the compressor. 

Bateman, G. C, "Cobalt Hydraulic Company," E. M. /., p. 
998, Nov. 18, 191 1, 1,000 words. Description of a Taylor 
compressor in which the air is drawn into a falling column 
of water. Compressed air is sold at 25 cents per 1,000 cubic 
feet at 120 pounds pressure. 

LowENSTEiN, L. C, "Centrifugal Compressors," series of arti- 
cles in the Gen. Elec. Review, p. 136, March, 191 2, 8 pages, 

7 illus. : theoretical discussion of the principles of the cent- 



BIBLIOGRAPHY 387 

rifugal compressor and the factors that influence efficient 
operation; p. 185, April, 191 2, 11 pages, 14 illus. Describes 
the application of centrifugal compressors to various kinds 
of work; p. 317, May, 1912, 8 pages, 7 illus. Discusses the 
rating of centrifugal compressors and the amount of power 
required for their operation. 

Anon., "Free-Piston Internal- Combustion Air-Compressor," 
Engineering J p. 285, March 1,1912, 2}^ cols. , 3 illus. Descrip- 
tion of a machine recently developed by Signor Matricardi, 
Palanza, Italy, in which a heavy piston is propelled from 
one end of a cylinder to the other, and during its motion 
compresses air in front of it. 

Sibley, Robert, "Power Computation of Rotary Air Compres- 
sors," Jour. Elec. Power and Gas, p. 270, March 23, 191 2, 
4>^ cols., 3 illus. An elementary discussion of the theoretical 
computation of power required in rotary air compression. 

LowENSTEiN, L. C, "The Centrifugal Compressor in the Man- 
ufacture of Gas," Am. Gas Light Jour., p. 204, March 25, 
191 2, 10 cols., 6 illus. Describes and discusses the principles 
of operation of turbo-compressors. Describes an automatic 
governing device in detail and cites a number of examples 
of the use of turbo-compressors. 

Anon., "Turbo-compressors in Practical Service," Iron Age, 
April 4, 191 2, 4 cols., 2 illus. Discusses the commercial 
promise of turbo-compressors and blowers and the efficiency 
of the different means of driving them. Also cites several 
installations. 

WiGHTMAN, L. I., "The Compressed Air Plant for Use at Mines," 
Min. and Eng. World, p. 757, April 6, 191 2, 4 cols. Dis- 
cusses the advantages and disadvantages of different types 
of air compressors, together with the difficulties encoun- 
tered with pipe lines. 

Davy, Norman, "The Gas Turbine," The Engineer (London), 
p. 421, April 26, 1912, 7 cols., 4 illus. The fifth of a series of 
articles on the gas turbine and contains a description of 
turbo-compressors as one of the accessory machines required 
with the gas turbine. 



388 MODERN TUNNELING 

Stone, S. R., "Increasing the Efficiency of Air Compressors/' 
Min. and Eng. World, p. 1039, May 18, 191 2. Discusses 
the means of preventing losses in air compression due to 
heat, clearance, and rarefaction. 

HoLDSWORTH, F. D., "Volumctric Efficiency of Air Compres- 
sors," E. M. J., p. 1028, May 25, 1912, 4 cols., i illus. Dis- 
cusses the unavoidable losses in air compression. Describes 
an apparatus for measuring the quantity of air delivered 
by the machine, which is the only way to secure an accurate 
determination of its efficiency. 

Anon., "Turbo Blowers and Compressors," The Engineer (Lon- 
don), p. 578, May 31, 191 2, 2}4 cols., 4 illus. Describes a 
20-stage machine installed at Manchester and discusses the 
advantages of turbo-compressors. 

Anon., "Turbo Blowers and Turbo-compressors," Iron and Coal 
Trades Rev., p. 874, May 31, 191 2, $}4 cols., 10 illus. Gives 
results of tests of a single-stage rotary blower and illustrates 
several turbo-blowers and compressors. 

COMPRESSION OF AIR 

Hiscox, Gardner D., " Compressed Air and Its Application," 

800 pages, 535 illus. Published by Norman W. Henley & 

Co., New York, 1901. 
Saunders, W. L., '^Compressed Air Information, 1903," 1165 

pages, 490 illus. PubHshed by Compressed Air Mag., New 

York, 1903. 
Saunders, W. L., '' Notes on Accidents Due to Combustion 

within Air Compressors," E. M. J., p. 554, April 11, 1903. 

Discusses the occurrence of accidents and the means for 

their prevention. 
Anon., ''Air Compression at High Altitudes," Min. and Min,, 

Vol. XX, p. 324, 1903, 1% cols. 
GoFFE, E., " Causes of Explosions in Air Compressors," E. M. /., 

p. 686, April 28, 1904, 4^ cols. An elaborate discussion 

of the causes of air explosions. Concludes that the chief 

one is probably the accumulation of dust which absorbs 



BIBLIOGRAPHY 389 

oil and when heated by the compressed air gives off explosive 
gases. 

Go w, Alexander M.," Ignitions and Explosions in the Discharge 
Pipes and Receivers of Air Compressors," Eng. News, p. 
220, March, 1905, 2}^ cols. Detailed results of an elaborate 
study of the causes of air-receiver explosions, with recom- 
mendations as to means of preventing them in the future. 

WiGHTMAN, L. I., '' Compressed Air: Its Production, Trans- 
mission, and Application," Proc. Eng. Soc. West Pa., Vol. 
XXII, p. 197, June, 1906, 42>^ pages. A detailed dis- 
cussion of the problems encountered in air compression, 
including stage compression, cooling devices, types of 
compressors and receivers. 

Cone, J. D., " Selection of Proper Air Compressor," Min. and 
Mm., p. loi, Oct., 1906, 6K cols., 6 illus. Discusses the econ- 
omic and mechanical considerations influencing the purchase. 

Peele, Robert, " Compressed- Air Plant for Mines," published 
by John Wiley & Sons, New York, 1908, 320 pages, 
112 illus. 

Brinsmade, Robt. B., " High z;5. Low Pressure for Compressed 
Air in Mines," E. M. J., p. 161, Jan. 18, 1908, t,}^ cols., 
illus. Contains a discussion of the effects of heat during 
compression, together with the devices for its removal. 

Redfield, S. B., '' Imperfect Intercooling and Efficiency of 
Compression," Comp. Air Mag., p. 4887, June, 1908, 11 
cols., illus. Discusses relation of cooHng to efficiency. 

Rix, E. A., " Compressed Air Calculations," Comp. Air Mag., 
p. 4894, June, 1908, 10 cols. Paper read before the Mining 
Association of the University of California. Discusses 
calculations" for design of compressed-air plants, to be used 
for a definite purpose, giving methods of procedure in cal- 
culating sizes, etc., of equipment. 

Anon., " Efficiency of Hydraulic Air Compression," E. M. J., p. 
228, Aug. I, 1908, 3 cols., illus. Abstract of article in 
Gluckauf, March 14, 1908, by P. Bernstein. Contains a 
description of a hydrauKc compressor installed in one of the 
mines at Clausthal, together with tests of its efficiency. 



390 MODERN TUNNELING 

Burgess, J. A., '' Explosion in Compressed-Air Main," Min. Sci. 
Press, p. 731, Nov. 28, 1908, 3>^ cols., letter to the editor, 
and also Comp. Air Mag., p. 5186, Feb., 1909. Describes 
an explosion at the Tonopah Mining Co., discusses the 
probable causes, and gives the precautions being taken to 
guard against a similar occurrence. 

Richards, Frank, " Probable Cause of Compressor Explosions," 
Comp. Air Mag., p. 5250, April, 1909, 2 cols. 

Redfield, Snowden B., '' Compressed Air Calculation Short 
Cuts," E. M. /., p. 1 163, Dec. 11, 1909. A chart by which 
M.E.P. and H.P. may be determined without formulae 
having fractional exponents, together with explanations 
of its use. 

Webb, Richard L., '' Cost of Producing Compressed Air at a 
Canadian Mining Camp," Can. Min. Jour., p. 102, Feb. 
15, 1910, 20 cols., 10 tables. 

McFarlane, Geo. C, " Compressing Air by Water," Min. Sci. 
Press, p. 281, Feb. 19, 19 10, 2 cols., illus. Discusses ways 
of utilizing water power which is so often available in 
mining districts for the compression of air and describes 
several devices for doing this. 

Anon., " Air Compressor Accidents in the Transvaal," Eng. 
News, p. 301, March 17, 1910, 2 cols. Discusses the probable 
cause of several explosions and gives the precautions taken 
to prevent their recurrence. 

Haight, H. v., " Steam-Driven Air Compressors in Cobalt," Can. 
Min. Jour., p. 209, April i, 1910, 3^ cols. Discussion of 
the paper by Richard Webb, Can. Min. Jour., Feb. 15, 
1910, p. 102. 

Redfield, S. B., ^' Efficiency of Compressed Air," Comp. Air 
Mag., p. 5656, May, 1910, 3 cols. Abstract of article from 
American Machinist, discussing the work done in compressing 
air. 

Anon., '' The Energy of Compressed Air," Comp. Air Mag., p. 
5775, Sept., 1910, 3K cols. Theoretical discussion of the 
energy employed in compressing air and the ways it is 
dissipated as heat. Taken from the American Machinist. 



BIBLIOGRAPHY 391 

Anon., '' Compressed Air Efficiencies," Comp. Air Mag., p. 5877, 
Dec, 1910, 3K cols. Discusses the efficiency of com- 
pressed air, especially when used in a rock drill. 

Saunders, W. L., '' Compressed Air Explosions," E. M. /., p. 
713, April 8, 191 1, also in Comp. Air Mag., p. 6028, May, 
191 1, 4 cols. Discussion of possible causes and means of 
prevention. 

Matthews, F. E., '' Air Cooling and Moisture Precipitation," 
Comp. Air Mag., p. 6201, Oct., 191 1, 3 cols., i table. Dis- 
cusses the effect of moisture in the air upon the difficulty 
of cooling it. Gives a table showing the amount of moisture 
in the air at different temperatures and degrees of saturation. 

Rix, E. A., '' Operation of Air Compressors," Min. Sci. Press, 
p. 13, Jan. 6, 191 2. Describes some of the main causes of 
loss in air compressors and suggests remedies for such as 
are not inherent in the design. 

Stone, S. R., '' Increasing the Efficiency of Air Compressors," 
Min. and Engng. World, p. 1039, May 18, 191 2. Discusses 
the means of preventing losses of air compression due to 
heat, clearance, and rarefaction. 

HoLDSWORTH, F. D., '' Voluinetric Efficiency of Air Com- 
pressors," E. M. J., p. 1028, May 25, 1912, 4 cols., 
I illus. Discusses the unavoidable losses in air compression. 
Describes an apparatus for measuring the quantity of air 
delivered by the machine, which is the only way to secure 
an accurate determination of its efficiency. 

Affelder, Wm. L., '' Air Compressor Explosions," Min. and 
Min., p. 651, June, 191 2, 2% cols., i illus. Some unique 
data upon the initial temperature of an air-compressor 
explosion furnished by a recording thermometer. 



COMPRESSED AIR ACCESSORIES 

WiGHTMAN,L.I.," Compressed Air: Its Production, Transmission, 
and Application," Proc. Eng. Soc. West Penna., Vol. XXII, 
p. 197, June, 1906, 42K pages. A detailed discussion of 
the problems encountered in air compression, including 



392 MODERN TUNNELING 

stage compression, cooling devices, types of compressors 
and receivers. 

Brinsmade, Robert B., " High vs. Low Pressure for Compressed 
Air in Mines," E. M. J., p. i6i, Jan. i8, 1908, 3^^ cols., illus. 
Contains discussions of the functions of intercoolers, re- 
heaters, and air receivers. 

Edit., " For the After Cooler," Comp. Air Mag., p. 5185, Feb., 
1909, lyi cols. Editorial discusses the value of the after- 
cooler in the prevention of compressed-air explosions. 

Anon., " Air Receivers," Comp, Air Mag., p. 5302, June, 1909, 4 
cols. Discusses the important functions of an air receiver. 

Richards, Frank, " Air-Receiver Practice," Comp. Air Mag., 
p. 5419, Oct., 1909, 7 cols., illus. Discusses the functions 
and efficiency of air receivers. 

Anon., " Tunnel Used for Compressed- Air Storage," Comp. Air 
Mag., p. 5443, 'Oct., 1909, 2 cols. Describes the use of an 
old cross-cut as an air receiver, giving a storage capacity 
equal to the output of the compressor for twenty-three 
minutes. 

Anon., '/ Compressor Pre-Cooler," E. M. J., p. 1081, Nov. 27, 
1909. Describes a simple, home-made pre-cooler consisting 
of a number of odd pipes kept constantly wet. 

Anon., ^'Compressor Pre-Cooler," iS.ikf./., p. 550, Sept. 17, 1910. 
Describes a pre-cooler consisting of a subway leading to a 
building having walls and floor of cocoa matting. 

Richards, Frank, " Things Worth While in Compressed Air," 
Comp. Air Mag., p. 6059, June, 191 1, 14 cols., illus. 
Describes economical devices in use at the Rondout and 
Yonkers' compressors plants, including after-coolers, drains, 
re-heaters, intake filters. 

Jones, J. W., '' The Inter-Cooler in Stage Compression," Comp. 
Air Mag., p. 6100, July, 191 1, 7 cols., illus. Abstract of 
an article in Machinery describing and giving the functions 
of inter-coolers. 

Richards, Frank, '^ Development in Compressed Air Power 
Storage," p. 6199, Comp. Air Mag., Oct., 191 1, 4 cols. De- 
scribes a means of maintaining constant pressure in a 



BIBLIOGRAPHY 393 

receiver, although volume of air is changing, by use of water- 
stand pipe. 

Richards, " The Disappointing Air Receiver," Comp. Air Mag., 
p. 6211, Oct., 1911, 4 cols. Some of the things an air receiver 
is popularly supposed to do but which it fails to do. 

Anon., ''A Novel Device for Re-heating Compressed Air for Use 
in Rock Drills," Engng. and Contng., p. 542, Nov. 22, 191 1, 
3 cols., 2 illus. Describes an automatic re-heating device 
using vaporized liquid fuel. 

Bateman, C. G., '' Electric Heater for Air-Line Drains," E. M. 
/., p. 831, April 27, 1912, 2 cols., I illus. Description and 
drawing of an electric heater used to prevent the freezing 
of the drains in the pipe Hne of the British Canadian Power 
Co. (Cobalt District). 

Anon., " Unloading Device for Air Compressors," The Engineer 
(London), p. 542, May 24, 191 2, 2 cols., 2 illus. Describes 
a device which, when the compressor is not working at 
full load, permits a portion of the air being compressed in 
the cylinder to flow back to the atmosphere or the inter- 
cooler, as the case may be. 

VENTILATION 

Thrikell, E. W., '' Adequate Ventilation," Min. and Mm., p. 

245, Jan., 1898, 4>2 cols. Abstract of a paper before the 

Midland Inst. Min., Civ. and Mech. Engrs. Discusses 

the ventilation required in mines and the influence of gases 

on men and lamps. 
Churchill, C. S., " Ventilation of Tunnels," The Engineer 

(London), Vol. LXXVIII, p. 799, 15 cols. 
Anon., " Improved Methods in Mine Ventilation," E. M. /., p. 

1059, Nov. 28, 1908. Discusses the use of cepitrifugal fans 

in mine ventilation. 
Fitch, Thos. W., Jr., " Mine Resistance," West Va. Coal Min. 

Inst., June 7, 1910. Discusses the calculation of mine 

resistance and gives a number of tables showing the friction 

in air- ways. 



394 MODERN TUNNELING 

AIR DRILLS 

Anon., ^' Burleigh s Pneumatic Rock Drill," E. M. /., Vol. 
VIII, p. 129, I col. 

Anon., ''Air Consumption of Rock Drills," E.M.J.,p. 648, Oct. 6, 
1906, ^ col. Gives figures for the air consumption of drills 
at 80 pounds pressure. 

Davies, W. a. T., " Mining Hard Ground," E. M. /., p. 779, 
Oct. 27, 1905, 8 cols., illus. Abstract of "The Science of 
Economically Mining Hard Ground Rock with Percussion 
Rock Drills and Compressed Air." Trans. Australasian 
Inst. Min. Engrs., Vol. II, No. 4, April, 1906. 

Sinclair, H.L.," Development of an Air Hammer Drill," E.ikf./., 
p. 714, April 13, 1907, 8 cols. Discusses some of the diffi- 
culties experienced with the early types of hammer drills 
and the modifications made to meet them. 

Patterson, Samuel K., "Air Drills and Their Efficiency," Min. 
Sci. Press, p. 467, Oct. 3, 1908, 2^ cols. Describes briefly 
several types of drills and outlines the methods to be used 
in determining their efficiency. 

Weston, Eustace M., '' Ways of Improving Piston and Hammer 
Drills," E. M.J., p. 549, March 13, 1909. Recommendations 
for improving the efficiency of drills based upon the recent 
South African Drill Competition. 

LiPPiNCOTT, J. B., '' Comparative Tests of Large and Small 
Hammer Rock Drills," Eng. News, p. 449, April 22, 1909, 
2 cols., tables. Give the results of tests made on the 
Los Angeles Aqueduct. 

Weston, Eustace M., " Surface Trials in Rand Stope Drill 
Competition," E. M. J., p. 998, May 15, 1909. Descrip- 
tion of the tests, giving a fist of the competing drills and 
some conclusions based on the surface trials. 

Anon., '' Ray Consolidated Mines (Arizona)," Min. and Min., 
July, 1909. Contains a discussion of the drilling equipment 
and methods used in these mines. 

Anon., " Hammer Drills for Small Sewer Work," Comp.Air Mag., 
p. 5464, Nov., 1909, 5 cols. Abstract from Eng. News of 
description of sewer construction at Bloomington, 111. 



BIBLIOGRAPHY 395 

Anon. /'Air Hammer Drills," Comp.Air Mag., p. 5539, Jan., 1910, 

I col. Discusses the merits of air hammer drills. 
Edit., " Respect the Rock Drill," Com p. Air Mag., p. 5633, April, 

1 9 10, Editorial. Some requirements for a good rock drill. 
Saunders, W. L., '' The History of the Rock Drill," E. M. J., 

p. 12, July 2, 1910, and also Comp. Air Mag., p. 5679, June, 

1 9 10. Brief history of pneumatic rock drill. 
HiRSCHBERG, Chas. A., '' History of the Water Leyner Drill," 

Min. Sci. Press, p. 596, Oct. 29, 19 10, i col. 
Dana, Richard T., and W. L. Saunders, " Rock Drilling," John 

Wiley & Sons, New York, 191 1, 300 pages, 125 illus. 
Harding, J. E., '' Piston or Hammer Drills," Comp. Air Mag., 

p. 5886, Dec, 1910, 3K cols. Discusses the advantages 

and disadvantages of the two types of drill. 
Marriott, Hugh F., " Mining in the Transvaal in 1910," 

E. M. J., p. 80, Jan. 7, 191 1, 10 cols. Contains a brief 

discussion of the stope drill competition. 
Anon., " Transvaal Stope Drill Competition," E. M. J., p. 163, 

Jan. 21, 191 1, 6 cols. Abstract of official report. 
Gordon, W. D., '' The Transvaal Stope Drill Competition," 

E. M. /., p. 356, Feb. 18, 191 1, 4^ cols. Comments on 

the report of the committee in charge, with a reply by the 

editor of E. M. J. 
Anon.,'' A Comparative Test for Air Drills " Coal Age, p. 842-3, 

April 6, 191 2, 3 cols., i illus. Describes a convenient 

method of testing the air consumption of drills. 

HYDRAULIC DRILLS 

Anon., '' Data of Tunnel Work in Europe," Min. Sci. Press, Vol. 
XL VIII, pp. 306, 322, 338, 1884. Contains a discussion of 
the advantages of the Brandt hydraulic drill with a de- 
scription of its use at several European tunnels. 

Talbot, F. A., "The Walski HydrauUc Rock Drill," E. M. J., 
p. 1278, June 18, 1910, and also Comp. Air Mag., p. 5582, 
March, 19 10, 6 cols. Describes a rock drill which utilizes 
water hammer effect produced when a moving column of 
water is suddenly stopped. 



396 MODERN TUNNELING 

ELECTRIC DRILLS 

Anon., " Meissner Electric Rock Drill," E. M. J., p. 759, Dec. 24, 
1898. This drill had a separate electric motor connected 
with the drill by a flexible shaft. 

Anon., " Low Cost Tunneling with Electric Drills," E. M. /. 
p. 759, April 20, 1905, yi col. Cost of driving 10 x 10 
tunnel in diorite where electric drills were used during Sept., 
Oct., and Nov., 1904. 

Palmer, Granville E., '^ Comparative Merits of Air and Electric 
Drills," E. M. /., Aug. 18, 1906. Gives disadvantages of 
electric drills. 

Barnes, H. B., " Air Drills vs. Electric Drills," E. M. /., p. 503, 
Sept. 15, 1906, 2}4 cols. Describes briefly and discusses 
the merits of several types of electric drills as compared 
with air drills. 

Chase, Chas. A., " Electric vs. Air Drills," E. M. /., p. 552, Sept. 
22, 1906, 1 3/^ cols. Gives the results from the use of electric 
drills in the Stilwell tunnel and in the Liberty Bell Mine. 

Richards, Frank, '' The Piston Action of the Electric Air DriU," 
E. M. /., p. 699, Oct. 13, 1906, 5 cols., 2 illus. Illustrates 
and describes the action of the ''Electric Air" drill. 

Anon., ^^Two Electric Drill Records with Costs," Comp. Air 
Mag., p. 5300, 2 cols. Drilling in slate, sandstone, and 
limestone with " Electric Air " drill. 

Gradenwitz, a., '' A Novel Rock Drill," E. M. /., p. 1181, June 
12, 1909. Describes a German electric drill having the motor 
connected directly with the drill. 

Anon., '' Fort Wayne Rock Drill," Min. Sci. Press, p. 548, April 
5, 191 1, 1/4. cols., illus. Illustrated description of a rotary 
hammer electrically driven rock drill. 

Hutchinson, R. W., Jr., " Modification of Mining Methods by 
Electric Machinery," Eng. Mag., p. 592, July, 191 1, nj^ 
cols., 4 illus. Discusses the development of the electric 
drill and describes several types which are giving satis- 
faction at the present time. 



BIBLIOGRAPHY 397 

GASOLINE DRILLS 

Anon., ''A Gasoline-Driven Rock Drill," E. M. /., Vol. LXXIX, 
p. 827, 1905, 2 cols., illus. 

Anon., '' The Scott Gasoline Rock Drill," E. M.J., p. 1008, Nov. 
21, 1908. Also Min. Set. Press, p. 852, Dec. 19, 1908, and 
Eng. News, p. 575, Nov. 26, 1908. Brief description of a 
two-cycle gasoline rock drill. 

Anon., " An English Gasoline Rock Drill," Eng. News, p. 538, 
Nov. 17, 1910, and also Compressed Air Mag., p. 5873, 
Dec, 1910, I col., illus. Illustrated description. 

DRILLING ACCESSORIES 

O'RouRKE, D. J., '' The Proper Shape for Rock Drill Bits," Mine 
and Quarry, p. 220, June, 1908, 8 cols., 10 illus. 

FiCHTEL, C. L. C.,'' Calumet and Hecla Drill Sharpening Device," 
E, M. J., May 29, 1909, 1,200 words, illus. Illustrated 
description of plant that handles 4,000 drills daily. 

DE Gennes, M., '' Selection and Use of Bits for Power Drills," 
E. M. J., p. 1183, June 12, 1909, 1,500 words. Discusses 
the different types and effect of size, shape, and cutting edge 
on the results. 

JuDD, Edw. K., " Design of Bits for Power Drills," E. M. /., 
p. 1220, Dec. 18, 1909. Discussion and comment on M. 
de Gennes' article in E. M. J., June 12, 1909. 

Weston, E. M., " Ejecting Sludge from Drill-Holes," E. M. /., 
p. 799, April 22, 191 1, I col., illus. Describes a method of 
cleaning holes by utilizing the plunger action of piston 
drills to force the sludge back through a hollow drill steel and 
out through a vent in the side of the steel near the chuck. 

McDonald, P. B., '' Drilling with Double Screw Columns," 
E. M. J., p. 1049, May 27, 191 1, i col. Discusses the 
advantages of the vertical column over the horizontal 
bar mounting for drills. 

Anon., " Long Column Arms in Tunnels," Mine and Quarry, p. 
540, Aug., 191 1, I col., illus. Describes the use of long arms 
on columns in tunnels of circular or oval cross-section. 

Blackburn, Ward," Notes on the Design of Drill Bits," E. M. /., 



398 MODERN TUNNELING 

p. 927, May, 191 2, 5 cols., illus. An article on the proper 
shape of drill bits. Advocates the use of sharpening 
machines. 

HAULAGE 

Clarke, W. B.,'' Electric Mine Locomotives," Min. andMin., p. 
389, April, 1901, 5^ cols., illus. Discusses things to be 
observed in choosing, operating, and caring for mine loco- 
motives. 

Clarke, W. B.,'' Electric Mine Haulage," Min. and Min., p. 252, 
Jan., 1902, 4^ cols., illus. Discusses design of electric 
motor equipment. 

Anon., '' Electric Haulage in Metal Mines," E. M. J., Vol. 
LXXVn, p. 324, 1904, 3 cols. 

Clarke, W. B., " Electric Mine Haulage," Min. Mag., p. 269, 
Oct., 1904, 14 cols., illus. First practical electric locomo- 
tive built in 1887 still in use in 1904. Describes some of 
the advantages of electric haulage and some of the more 
familiar types. 

Anon., " Mine Car Running Gear," £. Af./.,p.938, May 18, 1905, 
6^ cols., illus. Discusses the design of running gears for 
mine cars. 

SoLiER, A., '' Electric Traction in the Simplon Tunnel," Proc. 
Inst. Civ. Engrs., Vol. CLXVI, p. 465, 1906. Descrip- 
tion of the electric traction system adopted in the Simplon 
tunnel. 

Norman, Fred, '^ Advantages of Electric Haulage," Min. and 
Min., p. 383, March, 1908, 3 cols. Abstract of a paper read 
before the Y. M. C. A. Mining Inst, at Dubois, Pa., July, 
1907. Compares electricity with rope haulage, compressed 
air, and steam. 

DeWolf, E. C, " Haulage System at the Yak Tunnel," Min. and 
Met. Jour., June 26, 1908, 2^3 pages. A description of 
the method of handling ore and waste at the Yak tunnel. 

Foote, Arthur B., '' Dumping Waste with Locomotive Train," 
E. M. J., p. 711, Oct. 10, 1908. Describes a plow which 
could be attached at the end of a train of dump cars and 
push the rock over the edge of the dump when pulled by 



BIBLIOGRAPHY 399 

the locomotive, thus obviating the need of shifting the 
track so frequently. 

SiNNiBALDi, Paolo/' Electric Traction and the Simplon Tunnel," 
Proc. Inst. Civ. Engrs., Vol. CLXXVIII, p. 439, 1909. 
Description of the electric traction plant used in and about 
the tunnel. 

Anon., '' Cost of Compressed Air Haulage," Min. and Min., p. 
518, June, 1909, K col. Gives results obtained with com- 
pressed-air haulage at an industrial plant where the longest 
run is 2,400 feet. 

Johnson, J. E., Jr., ''An Improved Type of Mine Car Wheel," 
E. M. /., p. 1 180, June 12, 1909. Advocates tight-and- 
loose wheel construction. 

Perkins, F. C, " Electric Storage Battery Mining Locomotives," 
Min. Wld., p. 597, Sept. 18, 1909, i page, illus. Describes 
a German storage-battery mine locomotive. 

Saunders, W. L., " Compressed Air in Mines — Underground 
Haulage," E. M. /., p. 500, March 5, 1910, and also Comp. 
Air Mag., p. 5579, March, 1910. Discussion of a portion 
of D. W. B run ton's paper on Mining and Metallurgy in the 
United States, in Bull. A. I. M. E., j/, 1910. 

Anon., ''Internal Combustion Locomotives in Mines and for 
Surface Haulage," Petrol Rev., May 21, 19 10, 2^ cols., illus., 
and also Gas Power, p. 16, June, 1912, 3 cols., i^ pages, illus. 
Describes and gives some of the advantages of an English 
gasoline locomotive. 

Anon., ''Gasoline Mine Locomotives," Min. and Min., p. 30, 
Aug., 1910, iK pages, 3 cols., 3 illus. Discusses the advan- 
tages and disadvantages of gasoline locomotives, and de- 
scribes a German type. 

Anon., "Gasoline Locomotives for Mine Use," Min. and Min., 
p. 542, April I, 191 1. Results of the use of a gasoline loco- 
motive at the Mid valley Coal Co. mines, giving a table of 
costs. 

Sylvester, Geo. E., "Gasoline Motor Haulage," Min. and Min., 
p. 629, May, 191 1. Describes and gives results of the use 
of a gasoline locomotive in the mines of the Roane Iron Co., • 
at Rockwood, Tenn. 



400 MODERN TUNNELING 

Anon., ''Gasoline Motors for Mines," E. M. /., p. 292, May 20, 
191 1, 2 cols. Discusses some of the advantages of gasoline 
mine locomotives. 

Kenner, Alvin R., ''Mine Tracks," E. M. /., p. 1047, May 27, 
191 1. Discusses the laying of mine tracks and describes a 
method of extending rails near breast. 

Spahr, Jacob, "Rock Dump at Cokedale," p. 48, Min. andMin., 
Aug., 191 1. Illustrates and describes a rock dump con- 
sisting of a platform 22 feet long, carrying rails, pivoted at 
one end and having under the other end a wheel which 
travels on a curved rail with a radius of 22 feet. 

Simmons, Jesse, "Gasoline Mine Locomotive," E, M. /., p. 652, 
Sept. 30, 191 1, 2 cols., I illus. Description of mine locomo- 
tive for use in Trojan Mine, Portland (Black Hills) . 

Anon., " Rock Dump at Cameron Mine, Walsenburg, Colo.," Min. 
and Min., p. 158, Oct., 191 1. Describes a swinging rock 
dump. 

Anon., "Tireless Locomotives," Sci. Am.Supp., p. 388, Dec. 16, 

191 1. Discusses locomotives using superheated water in 
place of a coal fire and their possibilities for mining work. 

Barnes, H. B., "Storage Battery Mine Locomotive," E. M. /., 
p. 1278, Dec. 30, 191 1, and also in Elec. Review and Western 
Electrician, p. 52, Jan. 6, 191 2. Description of storage 
battery mine locomotives recently installed at Big Tive 
tunnel, Idaho Springs. 

Anon., "Testing Gasoline Mine Locomotives," Min. and Min., 
p. 341, Jan., 191 2, i^ cols., illus. Description of testing 
plant for gasoline mine locomotives. 

Anon., "Motor Trucks for Hauling Blasted Rock from City 
Aqueduct Tunnel, New York," Engr. Rec, p. 351, March 20, 

191 2, >^ col., 3 illus. A two-mile haul from shaft to dump 
on Contract 65 required facihties for rapid transportation 
of large loads through city streets. Gives the costs of this 
work. 

Van Brussel, J. B., "The Otto Internal Combustion Locomo- 
tive," E. M. J., p. 657, March 30, 191 2, i}4 cols., i illus. 
Description of a German gasoHne locomotive. 



BIBLIOGRAPHY 401 

King, A. F., ''Use of Gasoline Motors in Coal Mines," Coal and 
'Coke Operator, p. 355, June 6, 191 2, 2 cols. Describes and 
discusses the advantages and disadvantages of gasoline loco- 
motives for use in coal mines. 

Perkins, Fr.\nk C, ''Gasoline Locomotives for Underground 
Haulage," Engng. and Min. Wld., p. 1251, June 15, 191 2, 
3 cols., I illus. Discusses some of the advantages of gasoline 
locomotives for underground haulage. 

TUNNELING MACHINES 

Anon., "New Boring Machines for Tunneling," E. M. /., p. 969, 
Nov. 23, 1907, 7 cols. Discusses three types of tunneling 
machines, giving their defects. 

Bancroft, Geo. J., "A History of the Tunnel Boring Machine," 
Mining Science, Vol. LVHI, July-Dec, 1908, p. 65, 3^ 
pages, illus.; p. 85, 3 pages, illus.; p. 106, 2}^ pages, illus.; 
p. 125, 2}4 pages, illus.; p. 145, 2 pages, illus.; p. 165, 1)4 
pages, illus. 

Everest, H. A., "Tunnel Machines," Min. and Met. Jour., 
p. 4, Sept. 5, 1908, 5 pages, illus. Thesis, Col. School of Mines; 
an elaborate study of tunnel machines. Gives dates of pat- 
ents and results of experiments with the various machines. 

Hoskins, a. J., "Brunton Tunnel Machine," Min. and Met. 
Jour., p. II, Sept. 5, 1908. Part of an article on recent 
progress in tunneling machines, and gives a short description 
of the Brunton Tunneling Machine and the work accom- 
plished with it. 

Herrick, R. L., "Karns Tunneling Machine," Min. and Min., 
p. no, Oct., 1908, 2}4 cols., illus. Contains a general descrip- 
tion of the machine and gives tr^e results of a test run made 
with it near Denver. 

Anon., "Machine for Boring Rock Tunnels," Eng. News, p. 556, 
Nov. 19, 1908, 3 cols., illus. Description of one type of tun- 
neling machine. 

Tyssowski, John, "Trial of a Tunnel Boring Machine," Proc. 
Inst. Civ. Engrs., England, Vol. CLXXVIII, p. 411, 1909. 



402 MODERN TUNNELING 

Description of a test of the Terry, Tench & Proctor tunnel- 
ing machine at New York, June, 1910. 

Saunders, W. L., ''Driving Headings in Rock Tunnels," Bull. 
A. I. M. E., p. 337, Feb., 1909, 25 pages. Discusses 
methods of tunnel driving, with special reference to Euro- 
pean practice. Contains also brief descriptions of several 
tunneling machines. 

Tyssowski, John, ''Practical Test of a Tunnel Machine," E. M. 
/., p. 1296, June 26, 1909, illus. Describes the attempt to 
use a tunneling machine in connection with the excavation 
for the New York Central Railway Station. Describes the 
machine. 

Walton, Philip R., "Great Augers to Bore Holes in Moun- 
tains," Tech. Wld., p. 709, Feb., 191 2, 4 cols., illus. Popular 
description of one type of tunneling machine. 

ILLUMINATION 

Morrison, A. Cressy, "Acetylene Lamps," Comp. Air Mag., p. 
5180, Feb., 1909, 2 cols. 

Grimshaw, Robert, " Importance of Acetylene in Mine Opera- 
tions," Min. Wld., p. 779, Oct. 16, 1909, 2/i pages, illus. 
Describes German practice as abstracted from an article 
by R. Penkert, " Kohle und Erz." 

METHODS OF TUNNEL DRIVING 

See also Tunnel Descriptions. 

Bowie, August J., " Tunnels Used in Hydraulic Mining," Trans. 

A. I. M. E., Vol. VI, 1877. Portion of an article on hydraulic 

mining in California; discusses the selection of tunnel sites, 

grades, costs, methods of driving, timbering, etc., in gravel. 
Drinker, Henry S., "Tunneling, Explosive Compounds, and 

Rock Drills," published by John Wiley & Sons, New York, 

1878, 1025 pages, 1085 illus., several plates. 
Foster, C. Le Neve, "A Text Book of Ore and Stone Mining," 

pubHshed by Charles Griffin & Co., London, 1901, 730 pages, 

715 illus. 



BIBLIOGRAPHY 403 

Brunton, D. W., '' The Opening of Mines by Tunnels," E. M. /., 
Vol. LXXI, p. 147, Feb. 2, 1901, 2}i cols. Discusses the 
drainage of mines by tunnels, with some suggestions as to 
the methods of driving. 

Prelini, Charles, "Tunneling," published by Van Nostrand, 
New York, 1902, 307 pages, 150 illus 

Foster, C. Le Neve, ''The Elements of Mining and Quarrying," 
published by Charles Griffin & Company, London, 1903, 
300 pages, 280 illus. 

Gillette, H. P., ''Rock Excavation, Methods and Cost," 
published by M. C. Clark, New York, 1904, 370 pages, 
56 illus. 

Stauffer, David McNeely, "Modern Tunneling Practice," 
published by Eng. News, New York, 1906, 300 pages, i38illus. 

Adkinson, Henry M., " Advancing the Hot Time Lateral of 
the Newhouse Tunnel," E. M. J., p. 758, Oct. 17, 1908, 
Description of the methods used in this work. 

Edit., '' Speed in Small Drifts," E. M.J., p. 773, Oct. 17, 1908. 
Editorial discusses methods to be used in driving tunnels 
and drifts where speed is sought. 

Saunders, W. L., " Driving Headings in Rock Tunnels," Bull. 
A. I. M. E., p. 337, Feb., 1909, 25 pages, illus. Dis- 
cusses methods of tunnel driving, with special reference 
to European practice. Contains also brief description 
of several tunneling machines. 

HoGAN, John P., '' Progress on the Rondout Pressure Tunnel," 
Eng. Rec, p. 26, Jan. i, 19 10. Describes the methods 
employed on the Rondout Siphon in making the record 
run of 488 feet during Nov., 1909. 

H. R. S., "Freezing Ground in Tunnel Operations," Proc. 
Inst. Civ. Engrs., Vol. CLXXX, p. 361, 1910. A short 
description of driving through an unusually difficult piece 
of ground in the city of Paris by the freezing method. 

Hennings, F., "Long Railway Tunnels in the Alps," Proc. 
Inst. Civ. Engrs., Vol. CLXXXI, p. 506, 1910. A short 
but comprehensive review of the author's opinions on 
construction and operation of Alpine tunnels. 



404 MODERN TUNNELING 

Saunders, W. L., " Our Best Rock Tunnel Record/' Eng. Rec, 
p. 87, Jan. 15, 1910. Discussion of the methods used in 
making a record drive on the Rondout Siphon and a com- 
parison of them with European practice. 

Rollings WORTH, C. H., " Rock Tunnel Records," Eng. Rec, 
p. 797, June 18, 1910. Comment on the methods used at 
the Loetschberg tunnel and a comparsion of them with 
those at the Buffalo Water tunnel. 

Saunders, W. L., " Rock Tunnel Records," Eng. Rec, p. 224, 
Aug. 27, 1 9 10. Comparison of the methods employed in 
driving the Buffalo Water tunnel and the Loetschberg 
tunnel. 

Aston, C. W., ''The Elizabeth Tunnel (Methods)," Min. and 
Min., p. 102, Sept., 19 10, 6 pages, 4 illus., 4 tables. De- 
tailed description of the methods employed in this work. 

Anon., '' Tunneling Record on the Catskill Aqueduct," Eng. Rec, 
p. 441, Oct. 15, 1 9 10. Discusses the methods employed 
in making a record run (Sept., 19 10, 523 feet) on the Wallkill 
Siphon. 

Lauschli, E., '' Short vs. Long Headings in Tunnel Driving," 
Eng. News, p. 661, Dec. 15, 1910, i^ cols. Discusses 
the advantages of driving long headings. 

Anon., " The Top Heading and the Bottom Heading Method of 
Attack in Tunnel Construction," Comp. Air Mag., p. 5942, 
Feb., 191 1, 3 cols. Discusses the merits of the two S3^stems. 

Becker, Arnold, '' Bottom Heading Driving on the Hunter 
Brook Tunnel," Eng. Rec, Sept. 23, 191 1, 3,600 words. 
Also Comp. Air Mag., p. 6224, Nov., 191 1. Describes 
and discusses the advantages of the methods used in driving 
this tunnel. 

Anon., '' Comparison of Speed of Drilling the Laramie-Poudre 
Tunnel with Recent European Tunnel Records," Engng. 
Contng., p. 630, June 5, 191 2, 6% cols. Abstract from Proc. 
Am. Soc. Civ. Engrs., Vol. XXXVHI, p. 707, 1912, of a 
discussion by W. L. Saunders of B. G. Coy's paper on the 
Laramie Tunnel. Compares methods employed. 



BIBLIOGRAPHY 405 

DRILLING METHODS 
Bain, H. F., '^ Driving the Newhouse Tunnel," E. M. /., p. 552, 

April 19, 1902. Contains a description of the methods of 

drilling employed in this work. 
DiNSMORE, W. P. J., "Western Practice in Tunnel Driving," 

Mine and Quarry, p. 118, May, 1907. Contains a discussion 

of the methods of drilling used in the Ophelia tunnel. 
McFarlane, Geo. C, "Notes on Machine Rock Drilling," Min. 

Science, p. 291, Oct. 8, 1908, 3 cols. Gives a number of 

experiences in the use of rock drills and includes some data 

taken from actual practice concerning means of expediting 

this work. 
Aims, Walter L, "Methods Employed in Driving Alpine Tun- 
nels, the Loetschberg," Eng. News, p. 746, Dec. 31, 1908. 

Contains a description of the methods of drilling with a 

drill carriage. 
Anon., "The Roosevelt Tunnel," Min. and Min., p. 837, April, 

1909. Contains a description of the drilling methods used 

in driving this tunnel. 
Anon., "Ray Consolidated Mines (Arizona)," Min. and Min., 

July, 1909. Contains a discussion of the drilling equipment 

and methods used in these mines. 
LA\n[S, F., "The New Buffalo Water Works Tunnel," Eng. Rec, 

p. 802, June 25, 1910. Contains a description of the methods 

employed in drilling. 
Hulsart, C. R., "Excavation of the Walkill Pressure Tunnel," 

Eng. News, p. 406, Oct. 20, 1910. Contains a discussion of 

the methods of drilling employed in this work. 
Saunders, W. L., "Shallow vs. Deep Holes in Headings," Comp. 

Air Mag., p. 5995. A discussion of the factors that enter 

into the determination of the depth of holes. Compares 

American and European practice. 
Doll, ]M. G., "Strawberry Valley Tunnel of the Strawberry 

Valley Irrigation Project of Utah," Mine and Quarry, p. 483, 

May, 191 1. Contains a description of the methods of 

drilling in driving this tunnel. 
McDonald, P. B., "Drilling with Double Screw Columns," 



406 MODERN TUNNELING 

E. M. J,, p. 1049, May 27, 191 1, i col. Discusses the ad- 
vantages of the vertical column over the horizontal bar 
mounting for drills. 

Saunders, W. L., "Tunnel Driving in the Alps/' Bull. Am. Inst. 
Min. Engrs., No. jj, p. 507, July, 191 1. Contains a discus- 
sion of drilling methods with a drill carriage at the Loetsch- 
berg tunnel. 

Anon., ''Long Column Arms in Tunnels," Mine and Quarry, p. 
540, Aug., 191 1, I col., illus. Describes the use of long 
arms on columns in tunnels of circular or oval cross-section. 

Coy, B. G., ''The Laramie-Poudre Tunnel," Proc. Am. Soc. Civ. 
Engrs., p. 217, March, 191 2. Contains a description of 
the methods of drilling used at this tunnel. 

Anon., "A Remarkable Bore-hole," Coal Age, p. 778, March 23, 
191 2, 1% cols., I illus. Describes and illustrates a method 
of drilling a bore-hole to tap an old working containing 
water under 287 pounds pressure. 

Brunton, D. W., "Notes on the Laramie Tunnel," Bull. Am. 
Inst. Min. Engrs., No. 64, p. 357, April, 191 2. Contains a 
discussion of the methods of drilling used in driving this 
tunnel. 

BLASTING METHODS 

Daw, Albert W., and C. W., "The Blasting of Rock in Mines, 
Quarries, Tunnels, etc.," published by E. and F. N. Spon, 
London, 1898, 264 pages, 90 illus., 19 tables. 

Walke, Willoughby, "Lectures on Explosives," Wiley & Sons, 
New York, 1902, 425 pages. 

Anon., "Loading a Hole with Dynamite," E. M. J., p. 491, 
March 7, 1907, i col. Discusses mistakes commonly made 
in loading a hole and the methods of avoiding them. 

Stovall, D. H., "Position and Direction of Holes for Blasting," 
Ores and Metals, p. i, April 5, 1907. Discusses the greater 
importance of the location than the number of holes, and 
shows how the arrangement is determined by the character 
of the ground. 

Turner, H. L., "Loading Blast Holes," E. M. J., p. 433, Aug. 



BIBLIOGRAPHY 407 

29, 1908. Discusses the preparation of the primer and its 

position in the hole. 
Bell, Robt. N., ''A Selective Electric Fuse Spitting Device," 

E. M. J., p. 528, Sept. 12, 1908, illus. Description of 

electric firing board. 
Anon., ''Loading Blast Holes," E. M. /., p. 918, Nov. 7,. 1908. 

Gives reasons for placing the primer at the bottom of the 

hole. 
Hay, J. K., ''Loading Blast Holes," E. M. /., p. 971, Nov. 14, 

1908. Gives reasons for placing the primer at the top of 

the charge. 
CoLBURN, E. A., Jr., "Loading Blast Holes," E. M. /., p. 11 11, 

Dec. 5, 1908. Gives reasons for placing the primer at the 

bottom of the hole. 
McFarlane, Geo. C., "Loading Blast Holes and Driving Small 

Drifts," E. M. /., p. 225, Jan. 23, 1909. Discusses the 

position of the primer, the use of tamping, and describes a 

device to remove the tamping from a missed hole. 
Anon., "Details of Blasting Operations," Comp. Air Mag., p. 

5464, Nov., 1909, I'jA cols. Description for the layman of 

blasting methods. 
Thomas, H. Musson, "The Theory of Blasting with High Explo- 
sives," E. M. /., p. 352, Aug. 21, 1909. Discussion of 

blasting in s topes on the Rand. 
Walker, Sidney F., "Firing Shots in Mines by Electricity," 

E. M. /., p. 228, Jan. 22, 1910. A discussion of the causes 

leading to misfires and suggestions with respect to the 

selection of electric fuses. 
Hosier, M. T., "Preparations for Blasting," E. M. /., p. 1006, 

May 14, 1910. Discusses cutting the fuse, crimping primers, 

loading the hole, and spitting the fuse. 
Semple, Clarence C., "Where the Primer Should Go," E. M. /., 

p. 441, March 2, 191 2, 4 cols. Gives reasons for placing 

the primer at the top of the charge. 
Brown, H. S., "Where Should the Primer Go?" E. M. /., p. 

533, March 16, 191 2, i col. Gives reasons for placing the 

primer in the bottom of the hole. 



408 MODERN TUNNELING 

Semple, Clarence C, ''Where Should the Primer Go?" March 
23, 191 2, I col. Reply to the contention of H. S. Brown 
{E. M. J., March 16, 191 2, p. 533) that the primer should 
be placed at the bottom of the hole. 

Barbour, Percy E., "Where Should the Primer Go?" E. M. /., 
p. 825, April 27, 191 2, 3 cols. Sums up the recent discussion 
on this subject, quotes from various contributors, and 
concludes that the primer should always be placed last in 
drill holes, and that wherever there is a valid argument 
against putting it there, there are still stronger arguments 
for doing so. 

Anon., "Don'ts Governing Handling of Explosives in Mines," 
Min. and Eng. Wld., p. 915, April 27, 191 2, i col. Rules of 
the Oliver Mining Co. for employees. Twenty-five " don'ts." 

BLASTING SUPPLIES 

Oliver, Roland L., "Detonating Caps for Blasting," E. M. J., 
p. 682, Oct. 13, 1906, 13^ cols., 15 illus. Discusses the 
choice of proper strength of caps and the various ways of 
preparing the primer. 

Anon., "Blasting Gelatine," Min. and Min., p. 282, Jan., 1909. 
Discusses the use of "100 per cent, strength" gelatine 
dynamite at the Roosevelt tunnel. 

CuLLEN, Wm., "Gases from High Explosives," p. 297, Min. Set. 
Press, Aug. 28, 1909, 4 cols. Discusses the results obtained 
from a study of the gases given off from the gelatine dyna- 
mite used in Rand mines. 

Edit.", "Gases from Explosives and Mine Economy," Min. Sci. 
Press, p. 272, Aug. 28, 1909, i^ cols. Editorial comment 
on Mr. Cullen's article on page 297 of the same issue. 

Hodges, A. L., "Principles and Composition of Explosives," 
Min. Wld., p. 501, Sept. 4, 1909, 2 pages. Describes and 
gives the composition of different kinds of explosives. 

Anon., "The Necessity for Strong Detonators," E. M. J., p. 498, 
Sept. 10, 1910. Discusses the advantages from the use of 
strong detonators. 

Anon., "Explosives for Tunneling," Min. and Min., p. 159, Oct. 



I 



BIBLIOGRAPHY 409 

1910, 2}i cols., 2 illus. Discusses the factors to be consid- 
ered in the selection of an explosive for tunneling. 

Anon., ''Circuit Tester for Blasting," E. M. J., p. 1195, Dec. 17, 
1910, and also Min. Set. Press, p. 543, Oct. 22, 1910. De- 
scribes a galvanometer for testing a blasting circuit before 
firing. 

Hall, Clarence, W. 0. Snelling, and S. P. Howell, (U. S.) 
Bureau of Mines Bulletin ij, "Investigations of Explosives 
Used in Coal Mining," with a chapter on the ''Natural Gas 
Used at Pittsburgh," by G. A. Burrell, and an introduc- 
tion by C. E. MuNROE, 191 1, 197 pages, 7 plates, and 5 figs. 
Is intended especially for explosive chemists, but contains 
information of interest to all persons who have occasion to 
supervise the purchase or use of large quantities of explo- 
sives. Discusses the thermo-chemistry of explosives and the 
equipment and methods used by the Bureau of IMines in 
testing explosives. 

MuNROE, C. E., and Clarence Hall, "A Primer on Explosives 
for Coal Miners," (U. S.) Bureau of Mines Bulletin ly, 
61 pages, 10 plates, 12 figs. Discusses combustion and ex- 
plosion, the composition of explosives, the handling and use 
of explosives and of squibs, fuse, and detonators, and con- 
cludes with notes on the safe shipment and storage of explo- 
sives, and the requirements of permissible explosives. 
Reprint of (U. S.) Geol. Survey Bulletin 42^. 

Brinsmade, R. B., "Explosives Used in Mining," Com p. Air 
Mag., p. 6076, June, 191 1, 6 cols. Discusses the nature of 
explosives used in mining, and some of the factors influenc- 
ing their choice. 

RuTLEDGE, J. J., and Clarence Hall, "The Use of Permissible 
Explosives," (U. S.) Bureau of Mines Bulletin 10, 191 2, 34 
pages, 5 plates, 4 figs. Discusses the manner in which per- 
missible explosives can be used to best advantage in blasting 
coal. Is intended especially for coal miners and mine 
officials. 

Hall, Clarence, and S. P. Howell, "The Selection of Explo- 
sives Used in Engineering and Mining Operations," (U. S.) 



410 MODERN TUNNELING 

Bureau of Mines Bulletin 48, 191 2, 50 pages, 3 plates, 7 figs. 
States the characteristics of different classes of explosives 
and sets forth the results of tests showing the suitability of 
explosives for different kinds of blasting. The pamphlet is 
written for the information of all persons interested in the 
use of explosives for blasting rock. 

Snelling, W. O., and W. C. Cope, "The Rate of Burning of 
Fuse as Influenced by Temperature and Pressure," (U. S.) 
Bureau of Mines Technical Paper 6, 191 2, 28 pages. Dis- 
cusses the composition of fuse used by miners and the 
effects of differences of pressure, temperature, etc., on the 
normal rate of burning. 

Hall, Clarence, and S. P. Howell, "Investigations of Fuse 
and Miners' Squibs," (U. S.) Bureau of Mines Technical 
Paper 7, 191 2, 19 pages. Discusses the essential features 
of squibs and miners' fuse, and gives the results of various 
tests. The salient features of specifications adopted for the 
purchase of fuse for use on the Canal Zone, and suggestions 
regarding the transportation and use of fuse are given. 

Snelling, W. O., and Clarence Hall, "The Effect of Stem- 
ming on the Efficiency of Explosives," (U. S.) Bureau of 
Mines Technical Paper ly, 191 2, 20 pages, 11 figs. The gain 
in efficiency by the use of stemming was demonstrated by 
firing small charges of explosives in bore-holes in lead 
blocks. The pamphlet is of interest to all persons who use 
explosives for blasting coal or rock. 

Hall, Clarence, and S. P. Howell, "Magazines and Thaw- 
houses for Explosives," (U. S.) Bureau of Mines Technical 
Paper 18, 191 2, 34 pages, i plate, 5 figs. Describes a mag- 
azine and a thaw-house, each constructed of cement mortar, 
and gives the quantity of material required for construction. 
Points out the features essential for safe storage of explosives. 
Is of interest to persons who supervise the storage and use 
of large quantities of explosives. 

Anon., "Hydraulic Cartridge for Mining," Sci. Amer., p. 364, 
April 20, 191 2, i>2 cols. Describes a cartridge which 
expands by hydraulic pressure and is very useful for break- 



BIBLIOGRAPHY 411 

ing rock where it is essential that no shocks be imparted to 
the surroundings. 

MUCKING 

PoLHEMUS, J. H., ''Automatic Steam Shovel for Underground 
Work," Min. and Min., p. 575, July, 1909, 2 cols., illus.; and 
also E. M. J., p. 1056, Nov. 28, 1908, 2 cols., illus. Describes 
a steam shovel operating with compressed air in the mines 
of the Am. Zinc & Smelting Co., Carterville, Mo. 

Herrick, R. L., ''Mucking Problems in Tunnels," Min. and 
Min., Vol. XXX, p. i, Sept., 1909, i page, illus. 

HuLSART, C. R., "Excavation of the Wallkill Pressure Tunnel," 
Eng. News, p. 406, Oct. 20, 19 10. Contains a description 
of the methods of mucking employed in this work. 

Doll, M. G., "Strawberry Valley Tunnel of the Strawberry Val- 
ley Irrigation Project of Utah," Mine and Quarry, p. 483, 
May, 191 1. Contains a description of a stiff -leg derrick 
used for dumping muck cars on this project. 

Rice, Claude T., "The Use of Long- and Short-handled 
Shovels," E. M. J., p. 155, Jan. 20, 191 2, 3 cols. Discusses 
the merits of each type of shovel for mucking work. 

TIMBERING 

Sanders, W. E., Bernard McDonald, N. W. Parlee, and 
others, "Mine Timbering," published by Hill, New York, 

1907, 175 pages, 140 illus. 

Meen, J. G., "The Bracing of Tunnels and Trenches, with Prac- 
tical Formulae for Earth Pressures," Proc. Am. Soc. Civ. 
Engrs., Vol. XXXIII, p. 559, 1908, 60 pages. 

Crane, W. R., "Notes on the Use of Concrete in Mines," Con- 
crete and Constructional Engineering Mag., p. 39, March, 

1908, 6 pages, 7 illus. 

von Emperger, Fritz, "Notes on the Use of Concrete in Mines," 
Concrete and Constructional Engineering, p. 134, May, 1908, 
7 pages, 12 illus. 

Crane, W. R., "The Use of Concrete for Mine Supports," Con- 
crete and Constructional Engineering, p. 172, July, 1909, 
II pages, 12 illus. 



412 MODERN TUNNELING 

Fleming, W. S., "Selection and Framing of Timber," Eng. Min. 
Jour., Aug. 28, 1909, }4 page showing cuts. 

Anon., "Method of Making Water-tight by Grouting the Yon- 
kers Pressure Siphon of the Catskill Aqueduct," Engng. 
Con., Feb. 9, 1910, 1,500 words. Description of grouting 
machine, giving dimensional drawings and method of using 
in grouting the Yonkers Siphon. 

Humes, James, "False Set for Spiling Ground," E. M. /., p. 698, 
April 2, 1910, 3 col?., illus. Describes swinging false set 
pivoted at the center of the post. 

Herrick, R. L., "Tunneling on the Los Angeles Aqueduct," 
Min. and Min., Oct., 19 10. Contains an excellent descrip- 
tion of the methods of timbering used in the north end of 
the Elizabeth Lake tunnel. 

Rice, Geo. S., "Some Special Uses of Concrete in Mining," 
Cement, p. 432, Jan., 191 1, 12 cols. 

Young. Geo. J., "Driving in Loose Ground," E. M. J., p. 161, 
Jan. 21, 1911, 1% cols. Describes methods used on the 
Comstock Lode. 

Parrish, K. C, "Comparative Strength of Several Styles of 
Framed Timber Sets," E. M. /., p. 208, Jan. 28, 191 1, 
2 cols., illus. 

Anon., "Methods of Handling Running and Swelling Ground," 
Min. Eng. Wld., Dec. 9, 191 1. Describes customary prac- 
tice of timbering tunnels. 

ZiPSER, M. E., "Tunnel Lining, Catskill Aqueduct," Eng. News, 
p. 820, May 2, 191 2, 28 cols., 11 illus. A detailed descrip- 
tion of the methods of lining with concrete the tunnels on 
the Catskill Aqueduct of both the grade and the pressure 
or siphon types. 

McKay, Guy R., "Lining a Tunnel in Swelling Rock," Eng. Rec, 
p. 565, May 25, 191 2. Describes a concrete lining, reinforced 
by steel rails, placed in the Snake Creek tunnel. 
SPEED RECORDS 

Anon., "Mount Cenis Tunnel," E. M. J., Vol. IX, p. 344, K col. 
Contains a tabulation of the monthly progress on the 
Mount Cenis tunnel for the year 1869. 



BIBLIOGRAPHY 413 

Anon., '^ Rapid Tunnel Work," Min. Set. Press, Vol. XLVI, p. 
241, April 7, 1883, K col. 

Anon., ''Tunnel Work," Min. Sci. Press, Vol. LI, p. 292, Oct. 31, 
1885, yi col. Notice of record drive in Big Bend Tunnel, 
405 feet, in Sept., 1885, due to good drills and good 
ventilation. 

Anon., ''Big Bend Tunnel," Min. Sci. Press, Vol. LII, p. 237, 
April 10, 1886, }i col. 

Anon., "Records in Rock Tunneling," Eng. News,^.^^^, April 2, 
1908, 2]/4 cols. Contains a compilation of the maximum rates 
of progress at a number of American and European tunnels. 

Anon., "Rates of Progress of C. M. and St. P. Tunnel through 
Bitter Root Mountains, Montana," Eng. News, p. 9, July 2, 
1908, I col. Gives the progress on this work for March, 
April, and May, 1908. 

LiPPiNCOTT, J. B., "A New Record Established in Driving 
Hard Rock Tunnels," Eng. News, p. 570, Nov. 19, 1908, 
2 cols. At the Elizabeth Lake tunnel, Oct., 1908, 466 feet. 
Contains also a short list of other tunnel records. 

Anon., "Records of Driving Rock Tunnels and Some Comments 
on the High Cost of the Elizabeth Tunnel," Engr. -Contract- 
ing, p. 393, Dec. 9, 1908, 3^ cols. Contains a compilation 
of tunnel records both American and European. 

Herrick, R. L., "Tunnel Driving Records," Min. and Min., 
p. 422, April, 1909, 8^2 cols. Discusses the factors that 
make for rapid tunnel work and contains a compilation of 
tunnel records. 

Saunders, W. L., "European Tunnel Driving Records up to 
Feb., 1909," Trans. A. I. M. E., Vol. XL, p. 439, 1910. 
Contained in an article on driving headings in rock tunnels. 

, "American Tunnel Driving Records up to Feb., 1909," 

Trans. A. I. M. E., Vol. XL, p. 437, 1910. In an article on 
driving headings in rock tunnels. 

Anon., " Uncomparable Records," Comp. Air Mag., p. 5537, Jan., 
1910, 1% cols. Discusses the futility of attempting to 
compare different records of tunnel progress without con- 
sidering all the factors that influence them. 



414 MODERN TUNNELING 



SAFETY AND HEALTH 



Carter, T. L., '' Miners' Phthisis," E. M. /., Vol. LXXV, p. 474, 
March 27, 1903, 4 cols. Describes prevalence of miners' 
phthisis, which materially shortens Hfe of miners. Gives 
dust and oil (vaporized) as causes; powder gas, a possibility; 
and suggests free use of water as a preventive. 

SAUitoERS, W. L., ''Notes on Accidents Due to Combustion 
Within Air Compressors," E. M. J., p. 554, Apr. 11, 1903. 
Discusses the occurrence of accidents and the means for 
their prevention. 

CuLLEN, Wm., ''Miners' Phthisis, and Dust in Mines," E. M. J., 
p. 633, Apr. 25, 1903. Discusses dust in mines as one of the 
chief causes of this disease, and describes the methods used 
to prevent it. 

Anon., "Danger in the Cut-Off Hole," Min. and Sci. Press, Vol. 
LXXXVI, p. 405, June 27, 1903, i col. Describes danger 
of the cut-off hole, especially in shaft-sinking. 

Hoffman, Fred. L., "Fatal Accidents in Metal Mining," 
E. M. J., Vol. LXXVn, 1904, p. 79, 4 cols., p. 119, 3^^ 
cols. Statistics and discussion of causes of death. 

GoFFE, E., " Causes of Explosions in Air Compressors," E. M. /., 
p. 686, April 28, 1904, 4^ cols. An elaborate discussion 
of the causes of air explosions. Concludes that the chief 
one is probably *the accumulation of dust which absorbs 
oil and when heated by the compressed air gives off ex- 
plosive gases. 

Edit., '' Prevention, Miners' Phthisis," Editorial, E. M. /., 
Vol. LXXVni, p. 91, July 21, 1904, i^ cols. Mentions 
competition conducted by Transvaal Chamber of Mines 
for best methods of preventing miners' phthisis. Atomizer 
and water-drill reported favorably. Atomizer produces 
supersaturated atmosphere. Water lays dust at point of 
production. 

Edit., '' Miners' Phthisis," Min. and Min., p. 21, August, 1904, 
i^ cols. Editorial upon the investigation by the British 
Government into the causes of this disease. 



BIBLIOGRAPHY 415 

Gow, Alex. M., " Ignitions and Explosions in the Discharge 
Pipes and Receivers of Air Compress," £wg. News, p. 220, 
March, 1905, 2% cols. Detailed results of an elaborate 
study of the causes of air-receiver explosions, with recom- 
mendations as to means of preventing them in the future. 

Anon., " The Miner's Responsibility for Accidents," Min. Mag., 
Vol. XIII, p. 223, i>^ cols. 

Haldane, J. S., and R. A. Thomas, '' The Causes and Prevention 
of Miners' Phthisis," Trans. Inst. Min. and Met., Vol. XIII, 

P- 379, 1903-4- 

Burgess, J. A., " Explosion in a Compressed-Air Main," Min. 
Sci. Press, p. 731, November 28, 1908, and Comp. Air Mag., 
p. 5186, Feb., 1909. Describes an explosion at the Tono- 
pah Mining Co., and discusses the probable causes and 
gives the precautions being taken to guard against a similar 
future occurrence. 

Anon., " Prevention of Mine Accidents," E. M. /., p. 1088, Dec. 5, 

1908, 7 pages. Report of Committee of Am. Mining Con- 
gress to investigate laws relating to metal-mining. 

Edit., " For the After Cooler," Comp. Air Mag., p. 5185, Feb., 

1909, i}4 cols. Editorial discusses the value of the after- 
cooler in the prevention of compressed-air explosions. 

Anon., " A Pipe Explosion and a Runaway Compressor," Comp. 

Air Mag., p. 5188, Feb., 1909, i col. Describes a pipe 

explosion, which caused the compressor to run away and 

burst the fly-wheel. 
Richards, Frank, " Probable Cause of Compressor Explosions," 

Comp. Air Mag., p. 5250, April, 1909, 2 cols. 
, '' Flames in Compressed-Air Pipes,'^ Comp. Air Mag., p. 

5378, Aug., 1909, I col. Discussion of the causes of flames 

in compressed-air pipes. 
Bell, Robt. N., " Some 'Don'ts' for Explosives and Blasting," 

E. M. J., Vol. LXXXVI, p. 1281, Dec. 25, 1909, i col. 
Munroe, C. E., and Clarence Hall, " A Primer on Explosives 

for Coal Miners," (U. S.) Bureau of Mines Bulletin ly, 

pp. 61, 10 pis., 12 figs. Discusses combustion and explosion, 

the composition of explosives, the handling and use of 



416 MODERN TUNNELING 

explosives and squibs, fuse and detonators, and concludes 
with notes on the safe shipment and storage of explosives 
and the requirements of permissible explosives. Reprint 
of United States Geological Survey Bulletin 42 j. 
Anon., ''Accidents at Metal Mines," Mines and Methods, Jan., 

1910, pp. 10., illus. 

HoFEMAN, Fred'k L., " Fatal Accidents in American Metal 
Mines," E. M. J., p. 511, March 5, 1910. Gives statistics 
and discusses the need for legislation. 

Anon., " Air Compressor Accidents in the Transvaal," Eng. News, 
p. 301, March 17, 1910, 2 cols. Discusses the probable 
causes of several explosions and gives the precautions taken 
to prevent their recurrence. 

Wilson, H. M., and A. H. Fay, " First National Mine-Safety 
Demonstration, Pittsburgh, Pa.," (U. S.) Bureau of Mines 
Bulletin 44, with a chapter on " The Explosion at the Ex- 
perimental Mine," by G. S. Rice, pp. 75, 191 2, 8 pis., 4 figs. 
Describes the various exhibits at this demonstration; gives 
the addresses made and the names of the prominent visitors. 
Presents a summary of the investigations conducted at the 
Pittsburgh experiment station of the Bureau of Mines. 

Clark, H. H., " The Electrical Section of the Bureau of Mines, 
Its Purpose and Equipment," (U. S.) Bureau of Mines, 
Technical Paper 4, 12 pp., 191 1. Briefly describes equip- 
ment for testing electrical mining machinery, and some of 
the tests that have been made. 

Clark, H. H., W. D. Roberts, L. C. Ilsley, and H. F. 
Randolph, " Electrical Accidents in Mines, Their Causes 
and Prevention," (U. S.) Bureau of Mines, Miners' Circu- 
lar 5, 10 pp., 191 1, 3 pis. Presents suggestions as to 
measures that mine foremen, mine electricians, and miners 
should take to prevent electrical accidents. Also gives 
directions for the treatment of shock. 

Saunders, W. L.," Compressed Air Explosions, "E. M. J., p. 713, 
April 8, 191 1, and also in Comp. Air Mag., p. 6028, May, 

191 1. Discusses their possible causes and means of 
prevention. 



BIBLIOGRAPHY 417 

GooDALE, Stephen L., "Underground Safety Appliances," Min. 
and Min., Oct., 191 1. Illustrates and describes devices 
employed and scheme of working with reference to the mine 
of H. C. Frick Coke Co. 

Harrison, Geo. B., "Accidents in Mines Caused by Fall of 
Ground," Iron and Coal Trades Rev., Nov. 17, 191 1. Dis- 
cusses methods for reducing such accidents. 

Snelling, W. O., and W. C. Cope, "The Rate of Burning of 
Fuse as Influenced by Temperature and Pressure," (U. S.) 
Bureau of Mines. Technical Paper 6, 28 pages, 191 2. Dis- 
cusses the composition of fuse used by miners and the 
effects of differences of pressure, temperature, etc., on the 
normal rate of burning. 

Hall, Clarence, and S. P. Howell, "Investigation of Fuse 
and Miners' Squibs," (U. S.) Bureau of Mines, Technical 
Paper 7, 191 2, 19 pages. Discusses the essential features of 
squibs and miners' fuse and gives the results of various tests. 
The salient features of specifications adopted for the pur- 
chase of fuse for use on the Canal Zone and suggestions 
regarding the transportation and use of fuse are given. 

Hall, Clarence, and S. P. Howell, "Magazines and Thaw- 
houses for Explosives," (U. S.) Bureau of Mines, Technical 
Paper 18, 34 pages, 191 2, i pL, 5 figs. Describes a maga- 
zine and a thaw-house, each constructed of cement mortar, 
and gives the quantity of material required for construction. 
Points out the features essential for safe storage of explosives. 
Is of interest to persons who supervise the storage and use 
of large quantities of explosives. 

Clark, H. H., "The Factor of Safety in Mine Electrical Instal- 
lations," (U. S.) Bureau of Mines, Technical Paper ig, 191 2, 
14 pages. The author points out the factors that tend to 
make electrical installations less safe in mines than above 
ground, and gives some general directions regarding the 
adoption and maintenance of a high factor of safety. 

Rice, G. S., "Mine Fires, a Preliminary Study," (U. S.) Bureau 
of Mines, Technical Paper 24, 191 2, 50 pages, i fig. A com- 
prehensive summary of the causes of fires in mines and the 



418 MODERN TUNNELING 

equipment and methods to be used for preventing and 
extinguishing such fires. The pamphlet is addressed chiefly 
to mine owners and mine officials. 

Rice, G. S., ''Accidents from Falls of Roof and Coal/' (U. S.) 
Bureau of Mines, Miners^ Circular g, 191 2, 16 pages. Calls 
attention to the high death rate from roof falls in the coal 
mines of the United States and the need of constant watch- 
fulness by miners and mine foremen. 

Paul, J. W., "Mine Fires and How to Fight Them," (U. S.) 
Bureau of Mines, Miners' Circular 10, 191 2, 14 pages. Tells 
what the coal miner can do to prevent fires, and how incip- 
ient fires can be extinguished. 

Jones, L. M., ''Accidents from Mine Cars and Locomotives," 
(U. S.) Bureau of Mines, Miners' Circular 11, 191 2, 16 pages. 
Gives precautions that should be followed in traveling haul- 
age roads, and in handling mine cars. 

Anon., "Miners' Phthisis," So. Afric. Min. Jour., p. 153, March 30, 
191 2, i}^ cols. The first of a series of several abstracts from 
the official report of the Medical Commission's findings in 
their investigation of this disease. 

Affelder, Wm. L., "Air Compressor Explosions," Min. and Min., 
p. 651, June, 1912, 2j^ cols., i illus. Some unique data upon 
the initial temperature of an air-compressor explosion fur- 
nished by a recording thermometer. 

COSTS 

Ralston, W. 0.,"Cost of Tunneling at the Melones Mine, Cala- 
veras County, Cal.," Trans. A. I. M. E., Vol. XXVIII, 
p. 547, 1898. Gives description of the equipment, method 
of operating, and the cost of driving at the Melones 
Mine. 

Bain, H. F., "Driving the Newhouse Tunnel," E. M. J., p. 552, 
April 19, 1902. Contains a statement of the costs of this 
work for the year ending Aug. 31, 1900. 

BuNCE, Walter H., "Tunnel Driving at Low Cost," Min. Sci. 
Press, p. 60, July 11, 1908. Discusses the cost of driving the 
Chipeta Adit at Ouray, Col. 



BIBLIOGRAPHY 419 

Richards, C. H., ''Some Detail Tunnel Costs in No. 7 of the 
Los Angeles Aqueduct," E7ig. News, p. 542, Nov. 18, 1909, 
2 cols., tables. 

Hancock, H. S., Jr., ''Method and Cost of Constructing a 
Water Supply Tunnel through Rock by Day Labor," Engng.- 
Contng., May 25, 1910. Contains figures showing the cost 
of this work. 

Anon., "Some Published Costs of Tunnel Work in the Los 
Angeles Aqueduct," Engng.-Contng., June i, 1910, 2^ pages, 
illus. 

Herrick, R. L., "Tunneling on the Los Angeles Aqueduct," Min. 
and Min., Oct., 1910. Contains much information concern- 
ing the cost of tunneling on this project. 

Oke, a. Livingstone, "Standards of Work," E. M. J., p. 302, 
Aug. 13, 1910. Discusses the necessity of knowing all the 
factors that enter into each case before comparing two 
projects as to the amount of work performed, the kind of 
labor, and what is considered the standard of work for that 
particular class in that locality. 

Anon., "Bonus System on the Los Angeles Aqueduct," Min. and 
Min., p. 679, June, 191 2, 5 cols., illus. Discusses the rules 
of operation, the method of computing bonus, footage, and 
the earnings of the men. 

Lavis, F., "The New Buffalo Water Works Tunnel," Eng. Rec, 
p. 802, June 25, 1 9 10. Contains a schedule of the wages 
paid during the construction of this tunnel. 

Lauschli, E., "Hard Rock Tunneling," Eng. Rec, p. 719, Dec. 
17, 19 10. Gives a list of the wages paid on the Loetschberg 
tunnel work. 

Collins, Glenville A., "Ef!iciency of Engineering Applied to 
Mining," Min. and Engr. Wld., pages 869-70, April 20, 
191 2, 4 cols. Discusses the ways and means of applying 
"scientific management" to mining work. 



I 



CHAPTER XVIII 

RAILROAD TUNNELS 

INTRODUCTION 

In the last section of Chapter II a brief schedule of ^'Railway 
Tunnels" is given, all of which were built, for the most part, in 
solid rock. The chapters III to XVI, following, deal with the con- 
struction methods and equipment as applied to the tunnels, 
usually of comparatively small cross-section, which are involved 
in mining work and for the conveyance of water and the informa- 
tion given is confined, to a large degree, to cases where such 
tunnels are driven through solid and self-supporting rock. The 
information and conclusions given as to these types of small 
sized tunnels apply equally to the heading construction of the 
enlarged tunnels hereafter to be considered. This, and the suc- 
ceeding chapters, on Railroad Tunnels, on the other hand, 
deal with tunnels of comparatively large cross-section for the 
purpose of railway trafhc, for highway purposes, for canals, or 
for any other imaginable purpose in which the necessary cross- 
section is so large that the excavation cannot be performed as 
one operation but involves {a) The driving of a ^'heading" or 
advance drift, and (h) the subsequent enlargement of such 
heading (or headings) to the full cross-section of the finished 
work. 

For convenience in reference, all these large size tunnels are 
considered under the general title ''Railroad Tunnels" notwith- 
standing that their purpose or use may not be for railroad traffic. 
The name is merely meant to imply that the cross-section is of 
such size that the excavation has to be in stages instead of in 
one operation. 

It is perhaps worth noting that the first tunnel built in the 
United States was on the Schuylkill Navigation Canal. This 

420 



RAILROAD TUNNELS 421 

tunnel was opened for use in 182 1, was 20 feet wide, 18 feet 
high and 450 feet long. The widest tunnel in the world is also 
for canal purposes; this is the Rove tunnel near Marseilles in 
France which has a clear excavated span of 79 feet, a height 
of 51 feet and is 4I miles long. 

The following chapters on Railroad Tunnels take up the 
various methods which have been developed, starting with 
simple cases of tunnels driven through hard, self-supporting 
rock, and proceeding through the successively more complex 
conditions presented by loose rock, firm earth, loose running 
grounds and quicksands and lastly to the subaqueous tunnel, 
driven under a body of water through ground saturated and 
permeated with water under the head of the overlying river, 
estuary or arm of the sea under which the tunnel is driven. 

In this part of the work the word ''heavy" as applied to 
ground may be found to occur. To the miner this term is used 
to mean that the ground so designated is lacking in self-sustain- 
ing power, so as to require support to hold it in place when any 
excavation is made within it. To the extent to which the 
ground requires such support it is "heavy"; to the extent to 
which it is self-supporting it is ''light." Some grounds are both 
light and heavy; for example, certain clays, which, when first 
excavated will stand without support but which, after exposure 
to the air swell and disintegrate so that ultimately they are of 
the heaviest description and will bring almost unbelievable pres- 
sures upon the supporting timbering. 

In self-sustaining, non- weathering rock, the enlargement of 
the advance heading to the full cross-section is a simple matter 
of drilhng, blasting and mucking, but as the ground, whether 
rock of a loose, shattered or partly disintegrated character, or 
whether some variety of "soft" ground, by which is meant the 
various sands, gravels, clays or other materials not usually 
requiring the use of explosives in excavating, becomes less 
able to sustain or arch itself across any excavation or bore 
opened within it, then the process of excavation is complicated 
by tlie necessity for increasingly elaborate temporary support 
or "timbering" to retain the aperture excavated, until the 



422 MODERN TUNNELING 

permanent "lining" can be placed to receive and withstand the 
pressure of the earth. 

In loose rock the timbering is solely to hold the weight of 
crumbling rock or to prevent falls of loose rock from the roof, 
up to the point where the material will arch and thereby sustain 
its own weight, but in real soft ground the timbering must be a 
continuous, unbroken surface or "sheathing" covering the 
periphery of the excavation, both roof, sides and face and even in 
some instances the floor also. It is not uncommon to have to 
build tunnels through ground which will flow like a liquid under 
the influence of its pressure, such grounds are "quicksands" to 
the miner. In such a case no opening whatever can be made by 
the miner, until he has ready the means for extending the covering 
and support of such further area of soil exposed. These soils are, 
in effect, fluids having angles of repose not greatly removed from 
zero and must be treated as fluids. These grounds are known in 
tunnel parlance as "treacherous" and they will take their toll 
of human life on the slightest provocation. The writer remem- 
bers a case in which a tunnel was being driven in clean, sharp 
sand, which was so dry as to have little cohesion. An advance 
heading, close timbered, had been driven. In this a defective 
joint, or gap, between two face boards permitted a leak of sand. 
Two miners, experienced men, sent in to secure these boards 
must have disturbed or loosened one, without being prepared to 
replace it. The sand flowed in so fast that the men were buried 
before they could make their danger known to others, distant 
only a couple of hundred feet. 

Each kind of ground, however, has a certain, though possibly 
variable, from point to point, degree of cohesion. This gives 
such ground the power to sustain by arching action a certain 
load across a certain opening. Each such soil has also a definite 
angle of repose and a definite unit weight or specific gravity. 
Upon these basic characteristics will depend, whether consciously 
or unconsciously on the part of the practical miner, the methods 
of excavation and timbering which will be suitable to a given 
case. 

The main principle of tunnel building in such soft ground is 



RAILROAD TUNNELS 



423 



that no opening or excavation must be made greater in dimen- 
sions than that over which the ground will carry its own load 
unless such opening is at once supported by timbering. 

Each portion of such timbering must mrther be so con- 
nected with, and supported by, all other portions of the timber- 
ing system, that a structure well braced in every direction from 
external pressure results. For example, although perhaps pres- 




FiG. 8i. Tunnel timbering. American system. 



sures normal to the tunnel periphery are the chief ones to be 
provided for, it does not follow by any means that longitudinal 
bracing may be omitted. If that were done, and some longi- 
tudinal pressure, such as for example that from a run of ground 
at the face or from the blow of a flying fragment of rock being 
blasted, were to act on a portion of the timbering, such unsup- 
ported timbering would fall like a stack of cards and the collapse 
of the tunnel would follow. 

The methods of enlargement in soft ground are essentially 
the same as those used in driving the heading. The important 
thing is to prevent the ground from starting to move. 



424 MODERN TUNNELING 

As will be seen from the illustration, Figure 8i, the timbering 
of a tunnel resembles the hull of a ship. Outside against the 
ground, come the sheathing or "poling," corresponding to the 
skin of the ship's hull and serving the same purpose, namely, to 
exclude the soil, as the ship's skin excludes the water, and to 
transmit the pressure of the ground to the main timbers, which 
correspond to the frames and girders of the ship's hull. The 
softer the ground, the smaller its angle of repose the nearer it 
approaches a fluid the more nearly will the timbering be like a 
ship. 

The subject of Railroad Tunnels divides itself into two main 
headings: 

1. Economics of the proposition and design of structures. 

2. Construction. 

(a) Hard Rock Tunnels (self-sustaining) ; 

(b) Loose Rock and Soft Ground Tunnels (heavy) ; 

(c) Subaqueous Tunnels. 

The magnitude of the subject necessitates the elimination 
from detailed consideration of special problems in extremely 
long, deeply overlaid tunnels, as well as the various types of 
subways in cities which have been developed in connection with 
city transportation. 

Economics 
The primary object in the construction of a railroad tunnel 
as differing from small tunnels for mining, drainage or power 
purposes, is the conservation or production of revenue and 
so the relation between the cost and earning capacity of such 
an undertaking must be carefully considered. The total 
production cost of any tunnel, even under the most favor- 
able conditions, is so great that the only justification for the 
undertaking Hes in either, 

(a) PubHc necessity irrespective of monetary returns, or 

(b) Operating economy which will produce net revenue 

after deduction of operating expenses, mainte- 
nance and depreciation, ample to return interest 
on the investment. 



I 



KAILROAD TUNNELS 425 

It is obvious then that the first requisite is a broad consider- 
ation of each individual problem as presented, a preliminary 
estimate of probable cost, which must include not only the cost 
paid to the contractor for work executed, but also the amounts 
due to preliminary investigation,, engineering supervision and 
inspection, property and easements, cleaning up, cost of pre- 
liminary testing of structures in actual operation, and also 
cost of money, interest charges, financing, legal and general 
overhead expense. The other necessary factor in the deter- 
mination of justification, that of operating economy, is usually 
much harder to arrive at, but commonly there are certain 
outstanding reasons showing that the omission to incur these 
heavy costs would produce, as an alternative, a prohibitory 
operating condition. 

The most usual reasons for construction of tunnels are : 
(i) To shorten distance or reduce curvature. These cases 
are most common and such tunnels are usually short in length. 
A railroad following a valley finds it to be impossible to make 
bends without curvature greater than the allowable limit. The 
alternative then is to cut into the projecting land. In this case 
it is usual to extend the open cut approaches to such depth in 
rock or soil requiring flat slopes, until the estimated cost is equal 
to that of construction of a tunnel, at which points the portals 
will be estabhshed, except as modified by economies which might 
be obtained in future maintenance due to snow, slides, drainage, 
etc. 

(2) To reduce gradients. 

(3) To reduce extreme altitudes, the bad climatic conditions 
incident thereto and thereby to improve operating conditions. 

Reasons (2) and (3) are closely inter-related. They include 
the numerous class of "Summit Tunnels" introduced in crossing 
''divides." In cross-country railroad location it is the almost 
invariable practice to predetermine a controlling allowable gra- 
dient dependent on the general valley topography and conditions 
of operating traffic. The location leads up a valley, on the 
established gradients, to a point where the line must go under 
ground to cross to the similar valley point on the other side of 



426 MODERN TUNNELING 

the divide which has been reached at the controlling rate of 
grade which has been established for operating traffic in the 
contrary direction. Between those points a tunnel is essential, 
as the only alternative would be a break and increase in the 
adopted limiting gradient. 

(4) The elimination of grade crossings in city streets. In 
these cases there is commonly a direct return to productive use 
of surface areas previously occupied by trackage. 

(5) Crossing of rivers and waterways in cases where bridges 
would obstruct navigation or are not suited to local conditions 
or in other cases where the requisite spans are so great as to 
necessitate a bridge structure so costly as not to be warranted 
by the traffic accruing. 

Assuming then, that the analysis of the economic situation 
warrants the further prosecution of the project, the next step is 
the development of the design. 

DESIGN 

This may be considered under the following heads: 

(A) Geology; (B) Cross-section; (C) Alinement; (D) 

Lining; (E) Waterproofing of Lining; (F) Drainage and 

Pumping; (G) Ventilation; (H) Lighting. 

(A) Geology 

The preliminary exhaustive study of the geology of any 
tunnel problem is essential in the first place to the proper con- 
sideration of the economics as bearing on the probable cost of 
construction and feasibility of the undertaking; in the second 
place to the consideration of the type and design of the struc- 
ture and in the third place, to the contractor to determine the 
character and capacity of the plant necessary and the probable 
progress of construction as affecting his unit prices bid on con- 
tract, and his methods of laying out his work. 

A large part of the information necessary will be obtained by 
the geologist from extended surficial examination of soils and 
outcrops, but it is usually necessary to supplement this informa- 
tion by digging pits through overlying soils to rock, and by core 



I 



RAILROAD TUNNELS 427 

or Other drill borings, to determine at intervals the particular 
characteristics of the rock. Even with the most careful advance 
investigation, actual conditions in construction are commonly 
found materially different from the assumptions. It is there- 
fore strongly recommended to the engineer preparing contract 
plans and specifications for any tunnel, that as much positive 
information as can be obtained should be stated for the informa- 
tion and guidance of the contractor ; but that nothing whatever 
should be stated which is not actual fact and that no assumptions, 
opinions or conclusions of either the geologist or engineer should 
in any way be given except under definite agreement that the 
contracting parties accept no responsibihty for such opinions. 
The Courts of the United States and nearly every State have 
decisions in large numbers making liable the party responsible 
for any information given, which in the final result may have 
proved misleading or in error and thereby have occasioned greater 
cost and expense upon the contractor. 

An interesting illustration of the influence of the study of 
geology on the consideration of a great problem is given by the 
Channel Tunnel between England and France. Historical 
Geology shows that in prehistoric times the British Isles were 
continuous with the continent of Europe and that the present 
location of the gap between Dover and Calais was the divide of a 
highland. Subsidence has produced the channel way. The 
cretaceous formation is continuous and in all probability without 
fault, the dip of the strata rising on easy gradient from England 
to France, so that if a tunnel is started from England within the 
broad stratum of the Grey Chalk, which is practically free from 
flints, it can be carried through to France without penetrating 
the beds between the grey chalk and the underlying or over- 
lying strata which would undoubtedly yield great volumes of 
water and give uncertainty in the construction. This grey chalk 
is ideal material to excavate to full-size section with rotary 
cutting machines which break down the face and deliver onto 
conveyor belts for disposition into haulage at a convenient 
distance back of the working face. 

The advance study of the geology is necessary to the pre- 



428 MODERN TUNNELING 

determination of the probable cost of an enterprise. " To the 
designer it affords an understanding of the earth pressures as 
affecting the strength and character of the permanent hning; 
it will assist in the location of the portals and shafts and in the 
design of the approaches, and in the provisions he must make 
for proper drainage. To the constructor it affords assistance 
in the determination of his contract bid, as it gives information 
affecting the type and size of the drills, the compressed air and 
power plant, the probable earth temperature and the necessary 
ventilation to be provided, the probable volume and tem- 
perature of the water to be encountered, the extent and type 
of the timbering that will be required and the probable average 
progress of driving, all of which factors will affect the cost of 
the work. 

In many cases the geology is not the only or a controlling 
factor, as the tunnel has to be built directly between two given 
points, regardless of the geological conditions which lie between. 
Even in such cases, however, a knowledge of the rock structure 
is of great importance and value as affording a rational basis for 
a more accurate forecast of the probable cost in time and money 
of the proposed work. In other cases alternative routes may be 
possible, in some of which the geological conditions may be such 
that a great saving may be indicated, even though the route 
followed be not the shortest. A striking example of this is to 
be found in the Catskill water supply tunnels for the City of 
New York. A most careful and thorough analysis of the geology 
of the region traversed was made,* and the aqueduct tunnels 
were located so as to avoid crossing the East River at a point 
where the geology indicated that a fault zone would be inter- 
sected, while the tunnel to carry the gas mains of the Astoria 
Light, Heat and Power Company, at New York,t from one side 
of the same river to the other, had of necessity, on account of 
property ownership and the location of objective points of origin 

* "Geology of the Catskill Aqueduct," by C. P. Berkey. Published by 
The University of the State of New York. 

t See Paper No. 1359 of the American Society of Civil Engineers, by 
J. V. Davies. Transactions Am. Soc. C. E., Vol. LXXX, 1916, page 594. 



RAILROAD TUNNELS 



429 



and termination, to be driven on a line which intersected this 
zone, resulting in grave difficulties due to excessive influx of 
water at great pressure. 

(B) Cross-section 

The cross-section of a tunnel depends on three factors, 
namely: the function of the tunnel, the nature of the material 
penetrated and the method of construction. 

As to the function of the tunnel : the minimum internal cross- 
section must be large enough for the passage of the rolling stock 




Soction for yielding 
material that exerts 
6ide pressure- 



^^ 1 


Radius varies wlA | ^\^^ 


/^ 1 


distance between 1 /\ 


/ ^ 1 


Tracks ' /' \ 


-V 


Spacing of Tracks to ' 
Conform to Railway ' 
Standard ] 


4 > 
1 " 


o 


.t:iri 


V 8'0--* 

■r- -1 T *^ r 


, j-^*^ — 


— »H ^ r^ ^^ ?, 


^,\^- 


7T"JI( Subgrade '''. 


(5 "Drain Pipe 
of Cast Tron 


~^ 6 "Openings 



Fig. 82. Clearance diagram for single and double railroad track tunnels. 



or vehicles, as the case may be. Practically all railroads in this 
country are of standard gage and therefore every railroad tunnel 
must have clearance for standard rolling stock. This clearance 
has been standardized by the American Railway Engineering 
Association, see Figure 82, which shows the present (1920) 
standard. Track centers are usually fixed at from 13 to 14 feet 
for double-track construction. 

If the tunnel is to handle the traffic of a double-track line 
the alternative of one tunnel for two tracks or two tunnels each 
carrying one track will be presented. This is often a aifficult 
matter to decide. In self-sustaining rock the choice is unfet- 
tered by considerations of construction difficulties and the rela- 
tive advantages of each may be summed up thus : One double- 



430 MODERN TUNNELING 

track tunnel (a) allows more room for track repairs and renewals; 
(b) provides more space for clearing a wreck and (c) is generally 
cheaper than two single tunnels. Two single-track tunnels (a) 
give greater safety, as a wreck or derailment in one tunnel does 
not affect the other; (b) the ventilation is simplified, as a con- 
stant relation between the direction of the air current and that 
of the trains can be maintained, which cannot be done in a 
double- track tunnel, through which trains move in opposite 
directions. 

In respect to highway tunnels, the limiting size of automo- 
biles has not yet been fixed by statute, although this seems an 
inevitable development of the future. 

An exhaustive investigation into this matter, made by 
C. M. Holland, Chief Engineer for the New York and New 
Jersey Bridge and Tunnel Commission,* indicates that, with 
proper control and limitation of speed, automobiles require a 
clear headroom of 13 feet 6 inches above the roadway surface, 
including the maximum height of vehicle 1 2 feet under any con- 
dition of load, and clearance of i foot 6 inches to permit for 
possible necessity for jacking up. That the limiting outside 
width of an automobile body is to be taken as 8 feet, which is 
that agreed upon by manufacturers and State Highway authori- 
ties as the maximum desirable or necessary for highway opera- 
tion. An allowance beyond this width has to be made for 
irregular driving, clearance at curbs and clearance between lines 
of traffic. It has therefore been considered that for a single 
line of vehicle traffic there should be provided 13 feet between 
curbs; for a tunnel to serve two lines of vehicles in the same, or 
contrary, direction, the width between curbs should be 20 feet, 
while to provide for three lines of vehicles a width between curbs 
of 28 feet is to be considered the minimum, as those widths 
would provide adequately for mixed freight and pleasure vehicles. 
The design must consider the nature of the material to be pene- 
trated, which may range from the hardest and most durable 
rock to the softest and most liquid mud. In the former case no 

* Reports of the New York State Bridge & Tunnel Commission to the 
Governor and Legislature, N. Y., 1920 and 192 1. 



RAILROAD TUNNELS 431 

lining for the sole purpose of supporting the rock will be neces- 
sary, and the cross-section may be excavated to a shape dictated 
wholly by the clearance imposed by traffic requirements. In 
the latter case, while the clearance must be such as will admit 
the traffic, the cross-section of the tunnel Uning will be deter- 
mined primarily by the pressures imposed by the surrounding 
material. This is also true to some extent of all materials 
excepting those which are permanently self-sustaining. 

Before concluding the question of the type of cross-section 
selected in relation to the function of the tunnel, it may not be 
amiss to warn the engineer unfamiliar with the practical work 
of tunneling against a tendency, sometimes seen, of breaking the 
outside line of the tunnel cross-section with ditches, recesses, or 
duct chambers to carry minor utilities such as cables, drainage 
fines, etc. Anything which breaks the continuity of the outside 
periphery adds materially to the cost of the work, both in time 
and money, and should be avoided. 

As regards the influence of the method of construction on 
the cross-section this will usually be negligible, except in so far 
that the arch design must advantageously carry exterior pres- 
sures. The case is different, however, in the subaqueous tunnel 
driven with a ''complete" shield, in which case the cross-section 
will almost certainly be circular. The word ''complete^' is 
used in the previous sentence to distinguish the case from that 
in which a roof shield only is used, when the shape of the tunnel 
may be a regular horse-shoe cross-section or one with straight 
side-walls and an arched roof, as the engineer may elect. In 
ground which is not self-sustaining the problems of construction 
play a larger part in affecting the decision, but even so, the con- 
struction difficulties will probably be subordinate to the traffic 
requirements, especially since in most railway tunnels the 
extent of the soft ground offering exceptional difficulty will be 
a relatively small part of the total length, as those difficulties 
are usually confined to the vicinity of the portals. 



432 MODERN TUNNELING 

(C) Alinement 

In common with any other raihoad extension or improve- 
ment, the maximum rate of grade or degree of curvature allow- 
able for a tunnel is fixed by the requirements of operation rather 
than by constructional considerations. Wherever possible, tun- 
nels should be straight, as this simpHfies greatly the ventilation, 
reduces track maintenance and increases the safety of employees. 
Sometimes, it is true, in mountain country, spiral tunnels are 
introduced into a line for the purpose of gaining elevation, and 
in cities it is commonly necessary to follow lines of streets or 
properties which break up the continuity of the tangents. Due 
partly to condensation and partly to seepage of water, it is fre- 
quently the case that the rails in tunnels are damp and the trac- 
tive power of the locomotive and the braking effect is thereby 
reduced, and this fact should be given consideration in flattening 
the tunnel gradient below the general controlHng gradient of the 
railroad. 

A straight highway tunnel is desirable from the point of view 
of safety in use. The gradients should be kept, if possible, within 
a maximum of 3.5 per cent. 

Under no circumstances, for any kind of tunnel, should there 
be any level stretch, otherwise water will pool in the tunnel. 
While water will flow readily at a gradient of 0.25 per cent., it is 
better to provide a minimum gradient of 0.5 per cent., which will 
give free and rapid drainage flow. 

(D) Lining 

The two main questions which confront the engineer with 
regard to lining are: (i) Is any lining at all required and (2) if 
so, of what material shall it be built? When the tunnel is in 
loose rock or earth, as well as in solid rock tunnels in the lengths 
adjacent to the portals, or in clay or silt, as in the case of 
subaqueous tunnels, a lining is obviously essential. As a 
general rule it may be said that railroad tunnels that have 
not required a permanent lining, for some part of their length at 
least, are rare. Aside from providing for stability, in some cases 



RAILROAD TUNNELS 433 

considerations such as cleanliness or appearance may neces- 
sitate a lining, even where the permanent stability of the rock 
is certain. Many tunnels, among them some of the most noted 
in this country, were opened to traffic unUned, but subsequent 
weathering of the rock, vibration of trains, seepage of water or 
the exhaust of the locomotives resulted in falls of rock, which 
were a menace to safety and necessitated lining these tunnels 
under traffic at greatly increased cost, although sometimes 
this increased cost may have been warranted by the economy 
resulting from interest saved on deferred expenditures. 

As to the materials of which the lining should be built, the 
following have been used: (i) timber; (2) masonry; (3) brick; 
(4) plain concrete; (5) reinforced concrete; (6) concrete pre- 
cast blocks; (7) cast iron or cast steel; (8) structural steel. 
The choice of one or more of these m.aterials for lining a railroad 
or, to a less extent, a highway tunnel, will depend upon the com- 
parative availability and cost of the materials in place and on 
the earth pressure to be supported. 

In the early development of the railroads of the United States 
it has been common practice to line the rock tunnels with timber, 
when this would serve, in order to reduce the first cost of construc- 
tion, postponing the substitution of a more permanent lining until 
it could be paid for from earnings or from bonds floated on better 
terms after the traffic development of the property. With the 
increasing scarcity and rising cost of timber, its relatively 
short life, the menace of fire and, in particular, the excessive cost 
of relining a tunnel without interruption to traffic, it has become 
the practice to Hne such tunnels at the outset with material 
of a permanent nature. Where a temporary timber lining is 
built, for any reason, the excavation must be increased in order 
that there will be room enough within the timber lining to place 
the permanent lining, as it is generally impracticable to remove 
any of the original timber lining. If the second lining is designed 
so that no timber is to be incorporated within it, the original 
excavation will be particularly excessive, as will the cost of plac- 
ing concrete or brick masonry lining and packing behind it. If, 
on the other hand, the timber lining is to be surrounded to some 



434 



MODERN TUNNELING 



extent by a concrete Kning, the quantity of concrete will be 
unnecessarily great for the resistance it offers to ground pressures. 
In lining a tunnel permanently, during initial construction, these 
disadvantages may be obviated, and in many cases the cost of 
temporary timbering can be greatly reduced by intelligently 
planning the sequence of excavation and permanent lining so 
that the latter may be kept close to the finished excavation. 

The general system of timbering in use in this country — the 
so-called American system — is shown in Figure 83. Its chief 
advantages are simpHcity of erection and the reduction of the 
amount of timber used to a minimum. Its disadvantages are 




Cross Section. Longitudinal Section. 

Fig. 83. American system of tunnel timbering. 



tliat in heavy ground the last mentioned advantage tends to 
disappear, it is especially ill-adapted for unsymmetrical pres- 
sures and, finally, most rock excavation cannot be made with 
anything like the uniformity of outline of the timber sets, thus 
involving the necessity for much filling or packing back of the 
timber. In this system square timber is used almost exclusively, 
although round timber was formerly common and still is used 
for the posts. Certain climatic conditions may warrant the use 
of a preservative. If a subsequent concrete lining in which the 
timber may be embedded is contemplated, the timber used 
should be well seasoned. If round timbers are used for posts, 
the bark should be stripped to retard decay. 

Timber Hnings are generally restricted to cases where the 
ground is to all intents and purposes self-sustaining, and where 



RAILROAD TUNNELS 435 

the chief function of such lining is to prevent accidental falls of 
rock; consequently its design is chiefly empirical. 

With the more permanent types of Hning there is usually 
earth pressure to be resisted and the design of the hning there- 
fore takes on a more rational form, and may warrant, where 
possible, an analysis of the stresses. In a chapter such as this 
it is impossible to lay down any rules or to give any formulae 
which will enable the engineer to evolve a design suitable for 
the case he may have in hand. In the past, most tunnel lining 
designs have been based on precedent, experience and judgment, 
owing to our limited knowledge of the true character of earth 
pressures and the laws which govern them. Even with the 
most complete geological investigation it is impossible, at least 
with tunnels of any length or depth, to know precisely the nature 
of the rock, its stratification and other characteristics with 
enough accuracy to warrant any particularly refined analysis as 
to the probable earth pressures. The most a man can do is to 
get the best information he can as to the rock, make a design 
based on whatever theoretical considerations appear appHcable, 
check the tentative design by reference to other previously built 
tunnels of similar size and characteristics, then start the work, 
reahzing that the driving of the tunnel itself will disclose far 
more information than can be got in any other way and that he 
must be continually on the alert throughout the period of con- 
struction, so that he may modify the design of the Hning when- 
ever and wherever the conditions call for such action. As a 
suggestion it may be well to watch for faults in the rock, wet clay 
seams, or contact zones between contiguous strata which may 
result in unsymmetrical forces acting on the lining; the danger 
from rock, normally sound, becoming shattered from excessively 
heavy blasting and the presence of locally heavy water pressure. 
Further, there are many rocks (notably of volcanic origin) and 
soils which on exposure to the air between the excavation and 
permanent hning, weather and swell so as to exert extraordinary 
pressures on the Hning. In these cases extreme rapidity of Hning 
operations is essential to success. 

In the subjoined bibHography reference is made to several 



436 MODERN TUNNELING 

papers dealing with the mathematical side of tunnel lining 
design. 

Having determined or estimated, from theoretical consider- 
ations, aided by precedent, upon the extraneous pressures that 
the Hning will be required to withstand, the next step is to decide 
upon the material of which the hning may be formed. In the 
earliest times permanent lining was made of stone masonry, 
either ashlar, squared or rubble. With the increasing availabiHty 
of brick having a fairly high compressive strength, brick masonry 
began to displace stone masonry as a lining material, especially 
for the arch, owing to the greater ease of laying brick in cramped 
quarters, so that many early examples of tunnels will be found 
with stone masonry side walls and invert and brick arches. The 
present tendency, however, is away from stone and brickwork 
and toward concrete in some form, owing partly to the higher 
strength of the latter, partly to the fact that, being plastic, it 
conforms readily to the irregularities of the outside hues of the 
excavation, thus reducing leakage, and partly to the fact that a 
suitable hning of concrete can be procured at a lower cost, since 
a smaller proportion of skilled labor is required for this material. 
It is conceivable, however, that local conditions may enable a 
suitable masonry or brick lining to be laid at a lower cost than 
one of concrete and this should be looked into by the engineer 
before making a final decision. In fact, a comparison should be 
made of the relative costs of all the types of lining suitable for 
a particular tunnel before deciding which material to use. 

If a lining of concrete which has to withstand appreciable 
earth pressures is selected, it may be either plain or reinforced. 
In any design, due attention should be given to the inherent 
difficulty of placing concrete Hning in a tunnel. Very thin Hn- 
ings should not be attempted. For this reason it is worth while 
to sound a note of caution as to the matter of reinforced con- 
crete. The designer may be tempted at some time to achieve a 
figured saving by the use of reinforcement which, in reahty, will 
lead to added expense on account of the difficulty of placing and 
maintaining the reinforcement behind the forms and of placing 
the concrete properly around the reinforcement. The designer 



I 



RAILROAD TUNNELS 437 

must bear in mind that tunnel lining is usually placed under the 
disadvantages of cramped quarters, poor lighting, often large 
quantities of water and interference from timbers. The design 
therefore, should be one of rugged simplicity with a reasonable 
prospect of being built as planned, rather than one of such com- 
plexity as to require a constant vigilance in the inspection which 
cannot be assured. It seems well to point out that while a 
designer should not slavishly follow precedent, he must consider 
that should his reinforced alternative for a rugged simple Hn- 
ing prove to be a failure, it would have to be repaired or renewed 
under operation at greatly increased cost. Highly reinforced 
concrete is out of its element as a tunnel lining. 

It need hardly be said, although this section deals with 
design and not with construction methods, that nevertheless 
the method by which the Hning is to be placed, necessarily has a 
profound influence on the design; it should not be forgotten that 
the net cost of a concrete lining is dependent, not only on the 
quantity of concrete, but also on the extent of overbreakage, 
the cost of the forms, the labor of placing the concrete, the cost 
of waterproofing, if any, the backfilling or packing and other 
operations. Hence in some cases a thick lining, perhaps of 
leaner concrete, may be cheaper and better than a thin lining 
with its attendant backfilling and packing. In this connection, 
it may not be amiss to remind the reader of the possibilities of 
the pneumatic placement of concrete and even of the " cement 
gun," the latter being particularly useful where very thin linings 
are unavoidable, as well as for the repair of old linings. 

There is another form in which concrete may be used, namely 
in pre-cast blocks. This form is especially applicable for arches 
subject to symmetrical pressure and has several important 
advantages. They may be summarized as follows: (a) The 
quality and uniformity of the concrete may be made better than 
when placed in situ in the tunnel, (b) The contraction takes 
place before the material is placed in the tunnel, (c) A large 
part of the labor is employed on the surface w^here it is cheaper 
and more efficient than below, (d) The form work is reduced to 
a minimum, (e) Temporary timbering for support can often 



438 



MODERN TUNNELING 



be largely dispensed with, (f) The full strength of the arch is 
early attained, (g) A definite thickness of arch and a suitable 
surface for waterproofing is obtained, (h) The labor involved 
in rock packing behind the arch may be reduced. 




^!kc^^ 



For inverts and side walls, the advantages of pre-cast blocks 
are not nearly so pronounced, as block construction is best 
adapted for taking compressive stresses only. The size and 
form of these pre-cast blocks may vary with circumstances. 
For a single-track tunnel it may be possible to erect a full arch 
span in as few as three sections. The number would of course 



RAILROAD TUNNELS 



439 



increase with the span in order to keep the blocks from becoming 
unwieldy, although this may be compensated for by the use of a 
mechanical erector. The blocks may be plain or arranged to 
interlock and it is worth noting that some details of the latter 
type are protected by patents. Figure 84 ; this does not, however, 
exclude modifications which do not infringe on the patented 
features. 

As an illustration of what has been done along this line, the 
following table shows the size of the blocks which have been used 
on various important tunnels. 



Name ot Tunnel 


Span of Arch 


Size of Blocks 


Granges, Europe 


17 feet ins. 
14 feet 6 ins. 
37 feet ins. 
13 feet II ins. 


23ins. X4-6 insX 9-5 ins. 

12 ins. X 9.0 ins. X 18.0 ins. 

28 & 31 ins. X92.0X60.0 ins. 

24 ins. X60 ins. X32 ins. 


Arthur Pass, New Zealand 

Barrientos, Mexico 

Mount Royal, Canada 



The blocks in the Mount Royal were of the O'Rourke patented 
inter-locking type. 

As regards cast iron or cast steel as a lining material, the real 
field for these is in shield-driven tunnels, to which indeed, they are 
almost wholly confined. 

The form which this type of lining takes is that of "seg- 
ments," usually of a circle and consisting of the lining proper or 
"skin," from the four edges of which flanges project inwardly 
and normal to the skin, except that the short "key" has reversed 
angle joints longitudinally of the tunnel. The function of the 
flanges is to give construction depth to the lining and .thus enable 
it to carry the stresses and incidentally to afford a means of 
connecting the segments together by bolts in order to build up 
the lining, which is formed of successive "rings" of segments. 
These points are more clearly shown in Figure 85. 

This type of lining was originally used in England as "tub- 
bing" for lining mine shafts, and the first tunnel so lined was the 
seven-foot diameter Tower Subway for foot passengers across the 
Thames at London. This tunnel was also the first one driven 
with a circular shield which was the prototype of the modern 
tunneHng shield. 



440 



MODERN TUNNELING 




■pao«3.' 



RAILROAD TUNNELS 441 

This type of lining has several important advantages, which 
may be summarized thus: (a) For a given condition of loading, 
the thickness is less than that required with masonry or con- 
crete, thus reducing the quantity of excavation to be dene. 
(b) The full strength is developed as soon as it is erected. This 
makes it of especial value in shield driven work, (c) The labor 
of erection is less than with the foregoing types of lining, as it is 
a machine-operated process, {d) By caulking the joints and 
grummeting the bolts it may be made practically waterproof, 
even against a considerable head, (e) Since the Hning consists 
of successive rings of short length it is permanently erected and 
secured within the tail of the shield and thus the expense and 
hazard of timbering can be largely avoided, as the ground can 
be supported by the permanent lining without' delay. (/) This, 
together with (b), makes it possible to grout outside this lining 
promptly after it is erected, thus filUng every void and reducing 
settlement to a minimum, (g) The lining is durable and not 
subject to decay or appreciable corrosion. To increase its resist- 
ance to corrosion it is usual to hot dip the segments in a preserva- 
tive coating having a large proportion of pitch or asphalt before 
they leave the foundry. 

The disadvantages of iron as a Hning are its relatively high 
first cost as compared with other Hnings and its lack of flexibil- 
ity. By this latter is meant that, in its ordinary use in shield- 
driven work, the cross-section of the tunnel is almost always con- 
fined to a circle (although one or two examples of oval cross- 
section are to be found) and that as the lining consists of rings 
of uniform length, direction can be altered only by the use of 
special tapered rings, which are machine faced to definite angles 
of deflection. 

Ordinarily cast iron is the material used, but where special 
strength was required cast steel has been substituted. 

Notwithstanding that this type of lining has been used almost 
exclusively in shield-driven work, its possibiUties for other tun- 
nels should not be overlooked, especially for the arches of wet 
tunnels. 

This type is especially valuable and has been frequently 



442 MODERN TUNNELING 

Utilized for strengthening or waterproofing existing tunnel Knings 
of other material, which may show signs of being overstressed or 
which require waterproofing, and within which there is not 
enough room for any other type of reinforcement. As an 
internal reinforcement, where clearances have been extremely 
close, cast iron has been used in corrugated section form giving 
great strength for very shallow depth of construction. 

The detail of the design, namely: the number of segments, 
the length of the ring, the thickness of the skin and of the flanges, 
the depth of the flanges, the details of closing the ring by ''key," 
the question of machining the abutting faces of the flanges or 
of using wood packing strips (which is seldom if ever used in the 
present day), the size and spacing of the bolts and the method 
of rendering waterproof the joints and the bolts are matters 
which have to be studied to suit the circumstances of each case. 
Reference to previous successful examples of similar work will 
form the surest guide. Up to the present, judgment, experience 
and precedent have largely guided the designers of this type of 
tunnel, but of late years several attempts have been made to 
discuss the subject on more or less rational grounds and the 
reader is referred to such articles quoted in the BibHography. 
The table on page 443, however, giving the particulars of the 
cast-iron lining of several tunnels may be of value. 

It is to be noted that cast-iron lining is often supplemented by 
an interior lining of concrete extending wholly or partially around 
the perimeter. This is done to give a smooth interior surface, 
to increase the strength, and to afford protection against corrosion 
for the metal lining, especially the bolt heads and nuts. Since 
most iron-lined tunnels are circular in cross-section, while the 
clearance lines of the vehicles using them are approximately 
rectangular, there is usually a considerable amount of space at 
the sides not needed for traffic. This space is often utilized as 
benches, in which are embedded ducts for carrying electric power 
cables and telephone and telegraph wires. The top of the bench 
forms, incidentally, a good foot-walk clear of the traffic for 
maintenance employees and in cases of emergency. 

As will be understood, the possibility of water leaking into an 



RAILROAD TUNNELS 



443 



DETAILS OF CAST-IRON LINING FOR SOME SUBAQUEOUS 
TUNNELS 



Name of Tunnel 


Exter- 
nal Di- 
ameter 
of Ring 


Length 

of One 

Ring 


Thick- 
ness of 
Web 


Depth 

of 
Flange 


No. of 
Seg- 
ments 
in One 
Ring 
Exclud- 
ing Key 


Weight 
of Cast 
Iron in 
One Ft. 
of Tun- 
nel 


1 
Diam- 
eter of 
Bolts 
con- 
necting 
Seg- 
ments 


Hudson & Manhattan 
R.R., Hudson River, 
New York, 1906 


Ft. Ins. 
16 7 


Ins. 
24 


Ins. 


Ins. 
8 


No. 

9 


Lb. 
5,670 


Ins. 


Battery Tunnel, East R., 
New York, 1901 


16 81 


22 


li 


ih 


8 


4.540 


I 


Pennsylvania R.R., Hud- 
son R., New York, 1 906 


23 


30 


2 


II 


II 


11.594 


T •'' 


Blackwall Vehicular Tun- 
nel, River Thames, 
London, Eng., 1892. . . 


27 


30 


2 


12 


14 


14,784 


a 


Rotherhithe Vehicular 
Tunnel, River Thames, 
London, Eng., 1908. . . 


30 


30 


2 


14 


16 


16,845 


i^ 


Proposed Vehicular Tun- 
nel, Hudson R., New 
York, 192 1 


29 6 


30 


l| 


14 


14 


17,000 


If 



iron-lined tunnel is confined to the joints between the segments 
and to the bolt holes, which have an allowance for a clearance 
over the diameter of the bolt. The joints of cast-iron segmental 
lining are nowadays invariably machine faced to limit gages 
over nearly the entire area of all flanges. To provide for water- 
proofing, a narrow caulking groove is provided in each casting 
on the interior edge of each flange so that when two plates are 
erected together the two recesses oppose each other so as to 
make a caulking cavity of a slightly dovetailed form about 
I inch to I J inches deep and | to J inch wide. As every jointed 
structure will change its form upon imposition of earth pressures 



444 MODERN TUNNELING 

and these deformations extend over a considerable period of 
time before a final and stationary condition is reached, it is 
desirable that the waterproofing of the joints should be made 
in the first instance with a flexible fibrous or soft metalHc sub- 
stance which will permit repeated recaulking during this period 
of adjustment of form, after which the grooves may be finally 
filled and caulked solid with lead or the preliminary lead caulk- 
ing may be backed up by a final introduction and caulking with 
either a mixture of iron filings and sal-ammoniac (rust jointing), 
or cement mortar or any combination of these. The bolt holes 
are waterproofed by rings of hemp dipped in red lead, or of 
stamped or cast washers of lead placed under the iron washers — 
at both ends — around the shank of the bolts. These rings are 
called grummets. This process of caulking joints can by care 
and repeated recaulking be made to produce an almost abso- 
lutely water tight structure even in wet soil. The operation of 
waterproofing such a tunnel is best performed as a separate one, 
after the strains and stresses due to driving have ceased, as even 
slight movements destroy the efficacy of the waterproofing. In 
some cases the caulking has been done exclusively with rust 
jointing, but there is great danger of an inelastic joint material 
failing of its purpose when subjected to settlements and changes 
of form. 

As an example of the efficacy of the waterproofing in such a 
tunnel, it may be remarked that the Hudson River twin tunnels 
of the Pennsylvania Railroad, which are 23 feet in diameter and 
5000 feet in length, under a maximum head of 98 feet of water 
and in a silt which is saturated with water, give a leakage of 
only 200 gallons per 24 hours for each tunnel. 

A further development of metal fining, especially for sub- 
aqueous tunnels, is to be looked for in the use of structural 
steel. Several examples of this material used as lining are to be 
found. For instance, one across the Elbe at Hamburg; another 
across the Spree at Berhn and a short length of discharge tunnel 
under the Hudson River at Jersey City, N. J. The development 
of this material into a fixed type has not progressed to the point 
already reached by cast-iron lining, and the various examples 



RAILROAD TUNNELS 445 

cited differ widely in their details. For the most part, the 
structural steel examples now existing are ineffective designs, 
in that the details of the cast-iron type have been copied in steel 
and thus the valuable properties of the structural steel have been 
partly lost. When steel lining is designed along rational lines, 
however, certain valuable advantages are gained and these may 
be summarized as follows: (a) The tunnel is made completely 
and permanently w^aterproof by the enveloping skin of steel. 
{b) The elements of the lining are readily fabricated in any 
bridge shop, (c) A lining can be designed to be self-sustaining 
under any load w^hich may come upon it and to be capable of 
resisting any stresses, tensile or compressive, without deforma- 
tion except that due to the elasticity of the material, (d) For 
any given case the weight of the steel required is about one-third 
that of cast iron of equal strength; consequently the steel lining 
can be brought into the tunnel and erected in larger and fewer 
units, leading to an increased rate of progress and greater ease 
of waterproofing, (e) By means of electric welding, which has 
now become a perfectly practical process, the joints can be made 
absolutely waterproof, (f) The cost of such a lining, compared 
with cast iron or other material, depends obviously on local con- 
ditions and the prices of materials. For the city of New York, 
in the year 1920, structural steel lining in place has been esti- 
mated to cost about one-half that of cast-iron lining in place, 
for the same tunnel, {g) Steel as a material is inherently more 
reliable, more homogeneous and therefore safer to use than cast 
iron, which, on account of its defects, has been abandoned long 
since by bridge builders. 

It would be desirable, usually, to provide a secondary lining 
of concrete for a structural steel lining, to save the frequent 
painting which otherwise would be required and to afford a 
smooth interior finish to the tunnel. 

In any metal Hning its strength is a function of the depth of 
the flange. As the diameter of the tunnel increases the required 
depth of flange rapidly becomes greater and with a subaqueous 
tunnel the practical limiting depth of flange is reached when the 
tunnel reaches a diameter approximating 30 feet. In structural 



446 



MODERN TUNNELING 




RAILROAD TUNNELS 447 

steel, on the other hand, as the depth of flange is provided for by 
plates no limitation of the depth of flange is set, and conse- 
quently no limitation on the diameter of the tunnel, except such 
as may be imposed by the difficulty of adjusting the air pressure 
in the tunnel to balance the great difference in water pressures. 
Figure 86 shows the details of a steel lining. 

(D) Backing of Lining 

The actual kind of lining and its dimensions having been 
determined, it must be remembered that the tunnel as excavated 
will be of a cross-section in excess of the limits of the lining. 
This is done so that sufficient space is available for the lining and 
to avoid trimming, which is expensive. Even in a shield-driven 
tunnel there is a small, annular space outside the lining caused 
by the necessary clearance for the shield. Economically, over- 
breakage cannot be avoided and is frequently more pronounced 
in stratified than in igneous rocks. There is the further necessity 
for allowing space for timbering in certain kinds of material. 

Good practice does not permit the encroachment, within the 
predetermined limits of the lining, of any projecting portions of 
timbering or the rock itself. The space thus unavoidably left 
outside the limits of the permanent lining should be packed 
solid as the fining advances, in order to take up the soil pressures 
and so prevent any movement of the ground and to distribute 
properly the earth pressures over the permanent fining. The 
material generally used is rock from the tunnel excavation, 
carefufiy placed by hand. This is readily available when the 
lining is built in the first instance. In tunnels which have been 
lined after being put into operation it has been a frequent prac- 
tice to use cordwood or scrap timber for packing, the perma- 
nence of which seems disproportionate to that of the lining to 
which it is an adjunct. If it is desired to drain whatever water 
is present, this packing is left ''dry." In cases where it is 
desired to have a lining which is completely waterproof, it may 
be necessary to grout the packing with mortar forced by air 
pressure through pipes in the permanent lining. 

Speaking generally, for railway or highway tunnels piercing 



448 MODERN TUNNELING 

hills or mountains, the rock packing will be left dry and the 
water, if any, allowed to enter the tunnel through drains pro- 
vided for it. Usually the profile of the tunnel will be such that 
water thus entering will flow by gravity to one or both portals,, 
there to enter the general drainage system of the territory. In 
certain special cases, however, as where tunnels are built under 
waterways, the profile will be such that water entering the tun- 
nel cannot flow out by gravity. In these instances the engineer 
may have to choose between rendering the lining of his tunnel 
so waterproof that little or no water can enter or allowing it to 
enter as in the other case, conducting such water to a sump at 
the lowest point of the profile and pumping it thence to the 
surface. 

(E) Waterproofing Lining 

Apart altogether from the special case of the shield-driven 
subaqueous tunnel and considering only the rock or soft ground 
tunnel driven in the usual way, the methods of waterproofing 
such a structure are as follows: (a) The periphery of the tunnel 
is enclosed by a waterproof envelope or membrane, made up of 
several thicknesses or plies of a fabric such as cotton or felt. 
Each ply is put in place and covered with a layer of pitch or 
asphalt swabbed on in a heated and semi-liquid state. Another 
ply of fabric is laid on the first one and breaking joint with it 
and swabbed with pitch as before. This process is repeated 
until the desired number of plies is in place. The number 
depends on the head of water and may vary from three to eight. 
The various plies of fabric may be applied in long continuous 
roll form or when the working space is very constricted may 
be laid in sheets in every respect like laying shingles. Figure 87. 
A modification of the multiple ply system consists in using one 
ply only of a very heavy duck fabric treated with pitch and 
with broad overlap wherever the sheets of duck are joined. In 
this case when the waterproof sheet is laid all joints are seared 
with hot irons to effect a tight joint. In order to place the mem- 
brane it is usually necessary to build a thin concrete surface 
(called "sand walls") outside the net line of the permanent 



RAILROAD TUNNELS 



449 



invert and walls, on which to lay the fabric. After laying this 
type of waterproof in places where it is accessible it should be 






^ "S ° 1 







.2 
'5 

C 

c 

c 
o 



c 

o 

o 



protected by laying concrete for mechanical protection before 
back filling or packing. 



450 MODERN TUNNELING 

If the arch is built of concrete in situ it may be necessary to 
use a back form so that a fairly smooth outer surface is given on 
which to lay the membrane. 

Clearance has to be allowed between the timbering and the 
extrados of the arch in which the waterproofing can be laid and 
the back filling or packing over the arch has to be done with 
great care so that the membrane is not pierced by sharp corners 
of stones. With the small clearances usually allowed in tunnels 
the difficulty of laying such waterproofing, especially over the 
arch, is great. On the sidewalls and invert the difficulty is less. 
One grave fault in the membranous type of waterproofing is 
that a defective joint in laying up the fabric in wet ground may 
permit flow of water, which finding its way between the concrete 
lining and the fabric may percolate through the concrete lining 
at points quite remote from the original leak, giving considerable 
trouble to trace and stop. This trouble is one of those due to 
inefficiency of labor and lack of proper inspection oversight of 
construction. 

(&) Another form of waterproofing is to use brickwork set in 
a waterproof mastic consisting of hot melted asphaltic pitch 
mixed with clean sharp building sand and, or, limestone dust 
applied hot instead of in ordinary cement mortar. Here also 
sand walls will be generally needed on the invert and sidewalls, 
and back forms on the arches. For waterproofing arches, brick- 
work in mastic is more convenient than cotton or felt sheets, as 
the unrolling and handling of the sheets is awkward in the 
narrow clearance over the arch. 

(c) Many structures which have been intended to be water- 
proofed when built have proved to be not so after completion. 
A great deal of good has often been achieved by ejecting mortar 
under air pressure through pipes set through the Hning for this 
purpose. Notable examples of this are the aqueduct tunnels of 
the Catskill supply for the City of New York and the Astoria 
Tunnel. In the latter'case a pressure of 500 pounds per square 
inch was used and this was the first example where such a high 
pressure was attempted. The possibiHty of this method of 
waterproofing should be considered carefully in every case where 



RAILROAD TUNNELS 451 

it is desired to reduce pumping to a minimum. If the tunnel 
is to be waterproofed and the pumping eliminated it must be 
remembered that the lining may be subjected to the full head 
imposed by the water and the hning must be proportioned so 
that it is strong enough to withstand this pressure. If the water 
is to be allowed, under control (which in most cases is the proper 
policy), to enter the tunnel it is generally necessary that the 
arch and sidewalls, at least, shall be kept dry and the water 
should be made to enter the tunnel close to the bottom of the 
sidewalls. 

(d) Extensive use has been made of the so-called "Integral" 
method of waterproofing with very questionable success. This 
method depends on adding oils, soaps, lime or other materials 
to the mass of concrete as mixed, thereby reducing percolation. 

(e) Plaster coats. A certain measure of success has been 
attained in waterproofing tunnel structures by the surface 
appHcation of so-called Hydrolithic or other preparations in 
form of plastered coats. These usually consist of quick-setting 
silicates, or portland cement mixed with sal soda (Hot stuff), 
or other substances which will set quickly and will temporarily 
check the percolation of water through the voids in the concrete 
so long as to permit the sediment in the soil overhead washing 
into the watercourses and voids so as to choke themselves. 

(F) Drainage and Pumping 

The amount of attention that this phase of tunnel design 
necessitates from the engineer varies within wide limits but in 
general the problem is rather simple. 

It is particularly so in the case of a tunnel which has been 
driven and in operation for some time, and which, for one or more 
of the reasons previously given, it is deemed expedient to line. 
There should be no uncertainty about the amount of water to be 
taken care of, as the permanent provisions for pumping are not 
usually made until near the completion of the work when the 
amount can be actually gauged. In some geological formations 
there may be a seasonal variation. It is true that the engineer 
must decide, when he has the latitude so to do, whether or not the 



452 MODERN TUNNELING 

water is to be excluded from the lining or conducted through it 
by drains. If the quantities are Hkely to be excessive, attempt 
is usually made to exclude by waterproofing, otherwise free entry, 
reHeving pressures, is more usual. 

If the tunnel has been driven through a solid igneous rock or 
through a stratum of relatively impervious metamorphic or 
sedimentary rock, in a stratum which is thick compared to the 
cross-section of the tunnel, and so situated as to approximate a 
horizontal or convex bedding over wide areas, it is probably 
best to arrange to conduct through the tunnel lining such 
water as is flowing. It is only reasonable to assume that if 
the water is excluded by the Hning, it may accumulate consider- 
able hydrostatic head before rehef is obtained by its finding an 
outlet through some superimposed and more pervious stratum, 
or through seams, fault zones or other defined channels.- 

If the tunnel has been driven through water-bearing and at 
least fairly pervious sedimentary rocks, such as sandstones or 
shales, and particularly if the stratification is inclined to the 
horizontal and is known to outcrop at a level lower than that 
of the tunnel, at a not very remote distance, it would be in order 
to waterproof the tunnel lining, if conditions warranted the 
increased cost, over putting in drains and allowing the water to 
come into and run through the tunnel. It will be understood 
readily that the basis of this reasoning is that a comparatively 
low static head only will be sufficient to force the water through 
the surrounding rock rather than through the more impervious 
tunnel lining. 

A word of caution is given about omitting drains from the 
sidewalls in sections which, at the time of lining, may be 
dry. The course of underground waters is quite variable and 
good practice dictates the placing of drains at frequent and 
regular intervals, even although there may be, at the time, no 
apparent purpose to be performed. 

For a prospective tunnel which has to be both driven and 
lined the engineer must rely, for the basis of his estimate of the 
probable water flow, on such geological and topographical exami- 
nations as he can make or feels warranted in having made. 



RAILROAD TUNNELS 453 

Examination should be made of the outcrops on either side of 
the proposed tunnel, particularly in respect of the surface source 
of supply of underground waters which the tunnel is likely to 
tap. Inquiries also should be made of the flow in other tunnels 
in similar material and sometimes wells sunk to tunnel grade 
and pumped to gauge flow, may be of advantage as advance 
information. 

It is plain that the question of drainage will not influence 
the selection of a gradient for any railway tunnel — excluding 
subaqueous examples — of the length hmited in this chapter, 
namely not exceeding two or three miles. Even where a tunnel 
could be driven level it would not be so driven any more than 
would an open cut, but some inclination given to make it drain 
itself. In general then (again excepting subaqueous tunnels) 
the drainage problem resolves itself, with respect to water which 
is to be anticipated within the tunnel, to disposing of this water 
by gravity down a gradient which may lie anywhere between 
0.25 per cent, and the ruling gradient of the line. Occasionally 
two plus gradients converging in a vertical curve at a summit 
or two minus gradients converging in a dip may be found, but 
since the former miHtates against good ventilation during opera- 
tion, and the latter involves pumping drainage water, both will 
be avoided unless overbalanced by other advantages. 

In considering how best to conduct the water through the 
tunnel certain facts should be borne in mind. The cardinal 
principle in laying out drains is to place them so that they ofifer 
the minimum exposure to becoming clogged and the maximum 
accessibihty to inspection and cleaning. Another, it would 
seem, is that the drains be placed so that the passage of water 
over the invert is reduced to a minimum. 

In a single-track railway tunnel, either lined completely or 
w-lthout invert or wholly unlined, drains should be provided 
adjacent to the sides of the tunnel and the invert or bottom, as 
the case may be, slightly crowned in the center. In a highway 
tunnel, also, the drains might be similarly placed, as the passage 
of water across the driving surface to a middle drain would 
not be desirable. 



454 MODERN TUNNELING 

In a double- track railway tunnel which is unlined, in addition 
to the two side drains, there may be a center drain as well, 
especially if there is an appreciable drip from the middle portion 
of the roof. If the tunnel is fully or partially lined, however, 
there might be only two side drains, with the bottom crowned 
between them. 

The dimensions of the drains should be determined from the 
known or estimated quantity of water to be handled. It may 
not occur to everyone that, in most instances, the water which 
comes into a tunnel carries with it extremely fine mud or sand in 
suspension and often also alkaHne or metalKc salts in solution. 
These various substances are liable to be deposited in and at the 
outlets of the drains, so that these should be generously pro- 
portioned with this in view and regularly inspected. 

Subaqueous tunnels, in general, require that much attention 
be given to the subject of drainage. Since they are constructed 
to afford a means of crossing a body of water, there must be at 
least two descending gradients from the shores outward. It 
will be found usually that the physical conditions impose the 
selection of a gradient which is, or closely approaches, the limiting 
gradient of the line. This means that the water which enters 
the tunnel will readily flow to the low point, at which a sump is 
built. In the usual single-track subaqueous tunnel we have the 
following conditions which influence the drainage problem, 
namely : A practically waterproof lining , a smooth-lined invert , 
steep gradients, circular cross-section and relatively small clear- 
ance. These conditions have resulted in the general practice 
of draining such tunnels by a central drain. 

In subaqueous tunnels driven by shield and lined with metal 
rings it is possible to render the Uning Hterally waterproof and 
no pains should be spared in reaching this result. The reason 
for this is, not only to escape the constant expense of pumping, 
but tunnels driven through soft, water-bearing mud, as such 
tunnels often are, will be subject to a constant settlement if 
water is allowed to percolate through the lining. 

With such tunnels it is important to provide a safeguard 
against flooding from surface water and in large cities this danger 



RAILROAD TUNNELS 455 

is greater from bursting water mains and overflowing sewers than 
from the natural rainfall in the catchment area. It is good prac- 
tice to provide intercepting sumps of large capacity just within 
the portals of such tunnels to intercept the flood waters before 
they can flow to the lowest point of the tunnel. There will be 
a sump at the lowest point also and all sumps will be provided 
with pumps of large capacity to remove accidental flood waters, 
as well as with pumps of small capacity to remove the normal 
infiltration or seepage. In such tunnels the pumps, whether for 
emergency flood water or for ordinary infiltration, are usually 
driven by compressed air or electrically operated, but in either 
case they will be controlled by automatic starting and stopping 
devices, thrown into or out of action by the level of the water 
in the sumps. These devices can be adjusted to reduce the 
pumping to a short daily period of continuous work rather 
than to be pumping intermittently throughout the twenty-four 
hours. As an additional safeguard the pumping equipment is 
sometimes duphcated. 

In view of the increasing use of electric motive power on 
railroads, particularly in those divisions where there is most 
hkehood of employing tunnels, the question of the presence of 
water in the tunnels is of materially greater importance in respect 
of maintenance than simply the questions of draining and 
pumping. 

It is almost always the case that the walls of a tunnel are in 
the summer months cooler than the external air, and particu- 
larly in warm damp climates the condensation and drip in the 
tunnel keeps the rails and ties wet. Again if the drainage is 
not provided for and maintained adequately the ballast may 
also be wet. Under electrical operation, particularly with 
direct-current, there will usually be an escape of current through 
the running rails to the earth which will rapidly cause serious 
electrolytic corrosion of the base of rail, the fastenings and 
ultimately deterioration of the concrete lining, all of which 
should be studied with a view to possible elimination , 



456 MODERN TUNNELING 

(G) Ventilation 

In the earlier tunnels no artificial ventilation was provided, 
except that when intermediate shafts were used in the construc- 
tion, these were often lined with masonry, carried up above the 
surface of the ground and used as a means of escape for the 
locomotive smoke and gases. 

At the present time, where the traffic is frequent and heavy, 
it is becoming the practice to install mechanical ventilation on 
all but tunnels of short length. The old standards of comfort 
have changed and people are no longer content to suffer dis- 
comforts which at one time caused no comment, because con- 
sidered unavoidable. The presence of quantities of smoke and 
gases in a tunnel is, moreover, a positive menace to safety, as 
the operating crew of a locomotive or train may be overcome 
by poisonous gases under ordinary conditions, and even the 
passengers also, in the event of a stoppage or wreck. The same 
condition of danger applies with even greater force to the 
maintenance of way gangs. Unless the engineer can satisfy him- 
self that the tunnel, by reason of its short length, advantageous 
gradient or other contributing causes, will be able to clear itself 
readily of smoke and gases, he should give serious consideration 
to the question of mechanical ventilation. 

One fixed principle that can be stated is that a tunnel, the 
gradients of which rise from each portal to a summit within the 
tunnel, is certain to give poor ventilating conditions and for that 
reason such a profile should be avoided so far as possible where 
steam operation is contemplated, unless it is possible to install a 
ventilation shaft at the summit ; and even then the natural draft 
through this shaft may have to be supplemented by mechanical 
ventilation. 

A single-track tunnel will probably ventilate itself better 
than a double-track tunnel, as the train fills the bore more com- 
pletely and the piston action of the train helps greatly in clear- 
ing the tunnel, especially if all trains using it move in the same 
direction. 

The modern practice (based on the ''Saccardo" system) is to 
install fans or blowers and to force a strong current of air through 



RAILROAD TUNNELS 457 

an annular space surrounding the trainway on three sides. 
This induces the flow of an additional volume through the train 
space, thus either blowing the smoke and gases ahead of the 
train or clearing the tunnel quickly behind it.* 

In the case of highway tunnels in which a dense traffic of 
gasohne driven automobiles is to be provided for, a special prob- 
em is presented by the fact that such motors give off large 
amounts of highly poisonous carbon monoxide gas. This matter 
is a comparatvely new subject and is now under exhaustive 
study for the New York and New Jersey Interstate Bridge and 
Tunnel Commissions.! The results of this investigation, which 
will have high scientific and practical value, will be pubHshed 
at an early date; but it is now safe to say that, even with the 
dense traffic certain to use the long tunnels now projected to 
cross the Hudson River between New York and Jersey City, 
no insuperable difficulties in keeping the air wholly safe and 
even comfortable for human consumption are to be apprehended. 
The question is one of adequate dilution of the poisonous gas by 
mechanical ventilation within the tunnels, so as to reduce the 
carbon monoxide in the tunnel atmosphere to a limit of 4 parts 
per 10,000, which is found to be harmless for protracted exposure. 

(H) Lighting 
In the past, when railway tunnels were exclusively steam 
operated, when the tunnels were often built in locations remote 
from electric energy and when the volume of traffic and the conse- 
quent frequency of inspection and renewals were relatively slight, 
no attempt was made to provide for illumination after construc- 
tion. The locomotive headlight served the purpose during the 
passage of trains and the trackmen and inspectors relied upon 
lanterns. At the present time, due to the comparative density 

* "The Ventilation of Tunnels," by Chas. S. Churchill; International 
Engineering Congress in 1904 (see Trans. Am. Soc. C. E., Vol. LIV. part C, 
page 525). 

t Reports of the N. Y. and N. J. Interstate Bridge and Tunnel Commis- 
sions to the Governors and Legislatures of N. Y. and N. J. 1920 and 1921. 
Report of Chief Engineer C. M. Holland. 



458 MODERN TUNNELING 

of population in the East and Middle West and, in the moun- 
tain states, to the abundance of hydro-electric energy, which is 
distributed to great distances, it is almost always feasible to 
arrange for lighting a tunnel. Furthermore there is an increas- 
ing tendency to use electricity for motive power, which tends to 
make electric lighting readily available. Adequate lighting con- 
duces to safety in operation, lowers the cost and increases the 
efficiency of inspection and facilitates maintenance. It will be 
understood that unless the traffic is relatively heavy the lights 
should not be constantly burning, but arranged to be switched on 
as necessary. The wiring system should be as simple as possible 
and so placed and protected as to be immune from wet, sparks or 
gases, and well outside the standard clearance line of the rolling 
stock. Since the lights are of particular advantage in the event 
of clearing a wreck, they should be placed, so far as may be, so as 
to avoid being damaged in case such an accident should occur. 

All electric lighting circuit cables in tunnels must be laid in 
iron pipe with protected conduit boxes for making connection. 

In considering Hghting for highway tunnels there may be 
instances where, because of its short length, the tunnel will be 
illuminated adequately by natural light during the day. In 
general, short highway tunnels in isolated districts will not be 
lighted, in this respect being in the same state as the adjacent 
road. This indicates the need of having a footwalk at the side 
to safeguard pedestrians, and for policing purposes. In cities 
where traffic is dense and constant, every facihty is afforded for 
lighting such tunnels and this should be done, care being taken 
to give the maximum illumination with the minimum glare. 

CONTRACT BIDS 
In the consideration of the estimated cost of any railroad 
tunnel structure it should be noted that the ideas of cost and 
consequent bids of experienced contractors on tunnel work vary 
widely. In fact it is seldom that a group of bids on what would 
appear to be straightforward work do not vary as much as from 
50 to 100 per cent. As illustrations: a group of tunnels varying 
between 4000 feet and 400 feet in the construction of a rail- 



RAILROAD TUNNELS 469 

road in 1898, through the carboniferous strata of West Virginia, 
the quotations varied from $2.40 per cubic yard to $3.90 per cubic 
yard, or 62 per cent. In New York City subway tunnels 
awarded prior to the war, the bids on rock tunnel for one section 
ranged from $6.60 to $9.00 per cubic yard, a variation of 36 per 
cent.; another contract ranged from $9.00 to $15.00 per cubic 
yard, a variation of 72 per cent, above the low figure; the average 
bid by all contractors on this work being $12.60 per cubic yard. 
For another section, also before the war, bids ranged from $21 to 
$37 per cubic yard, a variation of 76 per cent;; and still another 
section bids ranged from $16.25 to v$3o per cubic yard, a variation 
of 83 per cent. 

Assuming in the case recited on page 541, that each con- 
tractor allowed (in preparing his figures) for a net anticipated 
profit of 20 per cent, above actual cost, then it would appear 
that based on previous experience, with accurate knowledge of 
prices of labor and materials, plant available and all overhead 
conditions defined, the average judgment of the group of 12 
bidders considered the actual cost of production was 25 per 
cent, higher than the low bidder believed to be practicable. It 
is usually the case, when a number of bids are received, that one 
or two contractors will tender exorbitantly high bids which may 
be due to various causes with which is interwoven the idea 
that they are not anxious to spend time and money to figure 
closely or to obtain the work but desire to be retained in the 
lists of bidders for future opportunities. EHminating such bids 
from consideration, it is commonly the case that the remaining 
bids will vary within 20 or 25 per cent, only, but at the same 
time there may be wide variation between those bidders upon the 
individual unit prices under classification schedules. The prin- 
cipal reason for this condition arises in the fact that a contractor 
after preparing his bids on all direct costs of labor and materials 
apportioned to each individual item, has a very large general 
overhead account, as well as his general power and fuel account, 
which is appUcable to the entire work, parts of which may be 
proceeding at irregular periods. It is seldom that the wise con- 
tractor will make this apportionment evenly distributed over 



460 MODERN TUNNELING 

each item but will on the other hand weight most heavily the 
items on which payments will be earliest received. The dis- 
tribution has to be carried out carefully and intelligently so as 
not to unbalance the bids improperly, since a large proportion 
of specifications and forms of contract provide that improper 
unbalancing between units of classification constitutes good and 
sufficient cause for rejection of any quotation so unbalanced. 



CHAPTER XIX 

CONSTRUCTION 

FOREIGN SYSTEMS 

Since this book is written particularly for the American 
foreman, superintendent, engineer and financier, it appears 
unnecessary to devote much space to any description of the 
various foreign systems of excavating, timbering and Hning soft 
ground tunnels. These systems have been evolved in the 
countries after which they have been named and are known, 
respectively, as the English, Belgian, French, German, Italian 
and Austrian systems. These various methods were slowly 
developed in the countries of their origin, over long periods of 
time, to meet the local and geological conditions. Excepting 
in special cases these methods are not used in this country and 
it seems outside the scope of this book to describe them. They 
are peculiarly adapted to very heavy rock pressures, such as have 
been encountered in the long deep Alpine tunnels and where, 
in consequence, there has been developed a class of tunnel work- 
men particularly skilled in this art.* 

These foreign systems for soft ground were developed dur- 
ing a period when mechanical appliances for driving and lining 
tunnels had not reached the stage of development at which they 
now stand. Consequently in those days, some elaborate mining 
system might have been necessary where the same work would 
be done nowadays in a much simpler manner, for example, by 
means of compressed air, with or without a shield. In this 
country it is probable that there will be few instances of condi- 
tions which will compel recourse to any of these foreign systems. 

* Cf. "Tunneling, Explosive Compounds and Rock Drills," by Drinker; 
"Modern Tunnel Practise," by D. M. Stauffer; "American Civil Engineers' 
Pocket Book," article by Alfred Noble and S. H. Woodard. 

461 



462 MODERN TUNNELING 

The far simpler American system has been thoroughly proved 
in rock and in soft ground tunnels for many years under nearly 
every kind of condition with complete success, and any engineer 
who is thoroughly conversant with the basic principles and with 
the possible modifications of this system has enough theoretical 
knowledge, at least, for this phase of any tunnel problem — 
other than shield driven — that may be presented. 

One of the main factors in the adoption of the American or 
some other foreign system of timbering lies in the fact that the 
skilled miners, upon whose efficiency the success of any method 
depends, obtainable in this country, are familiar with and expert 
in the use and capabilities of this system so that there is the 
greater certainty of successful results accruing from the employ- 
ment of the system which is well known. 

Following the outline stated at the beginning of Chapter 
XVII, the remaining pages will cover American practice as re- 
gards the construction methods and examples of (i) rock tunnels, 
(2) soft ground tunnels and (3) subaqueous tunnels. 

Before passing on to these separate classes of tunnel construc- 
tion, it may be well to devote a few words to the matters of 
tunnel survey work. 

Survey 

The location of a tunnel is a matter governed largely by the 
physical condition of each specific case and no hard and fast 
rule can be laid down. 

In order to determine the general fine and grade a reconnais- 
ance survey is requisite. This may be made quite perfunctory 
in territory already well mapped, as for example, by the United 
States Geological Survey. The route having been selected, it is 
usually necessary to know the exact distance and bearing 
as well as the elevations between the two portals. For some 
tunnels it may be easier to obtain such information by traversing 
than by triangulation. The latter method, however, is indis- 
pensable when the projected route crosses a waterway or other 
territory which is not readily traversed. This system reduces 
the actual work of taping to a minimum and substitutes therefor 



CONSTRUCTION 463 

the reading of angles which, with modern instruments and aver- 
aging repeated observations, can be carried to an extraordinary 
degree of precision. The accuracy of the work can be found 
from a "check base." This base hne is determined by averaging 
repeated measurements with standardized steel tapes, corrected 
for temperature and at constant tension and level and the base 
points established by solid monuments. Usually it is possible 
and desirable to locate the governing points of the triangulation 
so that they are removed from the active construction areas at 
the portals and thus are immune from being disturbed or covered, 
yet close enough to be readily used. In straight tunnels, where 
the shafts or openings are mutually visible, it will be good practice 
to locate instrument towers above points on this line as closely 
as can be calculated behind the respective shafts or portals, as 
the case may be, and then to adopt as the line of driving that 
between these two towers. This avoids subsequent possible 
errors of calculations, angle turning and the effect of local dis- 
turbances and movements of main reference points. 

In surveys to establish lines for the extension underground 
of a tunnel location so that the opposing headings when meeting 
may have a divergence of less than an inch in a distance of a mile 
or more, extreme care and accuracy in every operation are neces- 
sary and among others the following points must be carefully 
observed. 

All permanent points which are to be used either as base 
measurements or for transferring lines should be substantial 
monuments of bed rock or of cut stone or concrete embedded 
in the ground, in which a hole about one inch diameter has been 
drilled and a bronze plug cemented in, upon which the actual 
point is X-cut and drilled. 

Extending lines into the tunnels, it is usual to estabUsh all 
points both temporary and permanent in the roof and there- 
from to plumb down to working points in the floor. This is of 
course particularly the case when using top headings. The per- 
manent reference points must be established with great care as 
the work proceeds so as to avoid thereafter any necessity for 
repeating the running in of external lines after these tunnel points 



464 MODERN TUNNELING 

are once established. . Such points also should be drilled into the 
rock and bronze plugs inserted or in case of a fully timbered 
tunnel established on main timbers and thoroughly referenced. 
For temporary points, drill holes in rock plugged with wood or 
upon the main timber sets, using as the points a good sized nail 
drilled for plumb bob holes. A rough micrometer screw with 
sliding block, attached to roof timbers, is very useful in establish- 
ing points and a Hght screen consisting of a powder box over 
the front of which is a sheet of ground glass or a screen of tracing 
Hnen and inside the box an electric lamp, or candles, makes an 
excellent background for illuminating the hanging plumb bob 
lines. For the daily carrying forward of lines the plummet lamp 
is a very useful auxiliary but should not be considered sufficiently 
accurate for the permanent extension of the center line. 

The engineer must bear in mind that the atmosphere in 
tunnel work is almost always thick from fog and smoke, so that 
the length of sights is short and both temporary and permanent 
points must be established much more frequently than in out- 
side work. 

In some locations a single foresight can be established on the 
axis of the tunnel on the summit of the mountain under which 
such tunnel passes. This simplifies the laying out. In other 
cases lines have to be transferred from the surface down vertical 
shafts in which case plumb lines of small-sized hard brass wire 
are used making a wire line base as long as the shaft will permit 
on the axis of the tunnel below. In this case the plumb bobs 
used consist of lead weights cast with sheet metal wings pro- 
jecting so that when hung on the wires and oscillating in a tub 
(barrel cut in half is the best) of water they will quickly come 
to rest and remain stationary. At the top rigid and secure 
attachments must be made above the top of shaft for hanging 
the wires so that hanging freely each wire may be visible from 
the instrument set up on center line. The top suspension had 
better be made with sliding micrometer attachments and in use 
the two wires must be brought into transverse position so that 
the far wire is entirely hidden by the near wire from the instru- 
ment on center line. Transferring to the bottom the instrument 



CONSTRUCTION 465 

must be set up on a transversely sliding plate with micrometer 
screw and brought into perfectly true alinement with the wire 
lines and permanent points then established. 

In any case the engineer must carry forward his lines so 
close to the face that the foreman is furnished with two points, 
within clear sight at all times of the face, that he may hang his 
plumb bobs in Hne to chalk the center mark on the breast wall 
from which to set up drills or to lay out his timber sets for the 
next round in advance. Further details may be found in papers 
referred to in the bibhography. 

Since tunnels have to be driven without any ocular proof of 
their direction, complete reliance has to be placed on the instru- 
mental work to insure correct grade and ahnement. Conse- 
quently, all survey work has to be most accurately done and 
requires extreme care, patience and skill on the part of the aline- 
ment corps. The basic principles of laying out curves and tan- 
gents and of levelling apply as on the surface, but the engineer 
will have to exercise some resourcefulness to do his work in a 
thorough manner and at the same time keep from interfering 
with the progress of the actual construction. 

PLANT INSTALLATION AND EQUIPMENT APPLICABLE 
TO ALL CLASSES OF ENLARGED TUNNELS 

(A) Plant 

Generally the plant necessary is the same as that installed 
for the heading or small tunnels previously considered, except 
that the larger and more extended operations necessitate a large 
increase in the power employed and the use of mechanical means 
for economical execution of the work. 

Supplementing the resume in Chapter IV of the various 
kinds of energy and their applicabihty to tunnel operations, the 
following points are to be noted : 

There are, not infrequently, cases of short railroad tunnels 
in rock when it is advantageous and usual to drill and muck 
entirely by hand labor and omit the hauling in, location and 
operation of a power plant. These cases occur when the rocks 



466 MODERN TUNNELING 

are shales, soft sandstones or such other grades as may be easily 
drilled and will part readily under blasting. The results depend 
very largely on the experience and efficiency of the labor 
employed. The capital charges are reduced to a minimum, 
haulage can be done by hand labor in the heading and by mules 
in the enlarged tunnel, and under competent direction the unit 
costs will, in such cases, compare most favorably with a power 
operated layout and while the progress may not be quite as 
rapid, it is seldom in a railroad construction that the short 
tunnels constitute any controlling factor in the time of com- 
pletion of the undertaking. 

In the early days of machine drilHng, steam was often used 
directly to drive the drills and, in some cases, for short tunnels 
economy may still be obtained by this practice. It has serious 
disadvantages: thus, it involves long Hues of piping hot enough 
to burn and yet subject to great loss of heat from radiation; the 
exhaust steam from the drills makes the working place most 
uncomfortable and even dangerous. 

In cities or other places where electric energy is readily avail- 
able and the supply dependable, electricity has many advantages. 
It certainly reduces the prime cost of the plant and only as much 
power as is consumed during the progress of the work has to be 
paid for. The reduction in the amount of plant required may 
result in the work being started earher than would otherwise be 
possible. This would be true especially if electricity was the 
only kind of energy used. The disadvantages are the habiHty 
of interruption of the power supply from numerous and obvious 
causes. When not only the surface plant but the equipment in 
the tunnel itself is electrically driven, we have the added danger 
from conductors which may be poorly insulated and insecurely 
strung, the great aptitude for getting out of order which elec- 
trical apparatus at present has and the susceptibiHty of electric 
motors to the usually wet tunnel atmosphere. Electrical appa- 
ratus does not admit of receiving the crude treatment usually 
accorded to ailing machines by tunnel workers. 

Where fuel is costly and electric energy can be advantage- 
ously obtained; particularly by the purchase under contract of 



CONSTRUCTION 467 

power from local power-producing sources, considerable econ- 
omy may be effected by using electric drive for compressing air 
and other uses of the plant. 

As regards internal combustion engines, using any form of 
petroleum product or producer gas engines, it must be admitted 
that these all have possibilities for ultimate economies in the pro- 
duction of power, particularly in regions where the grades of 
fuel are obtainable. However, they have, to date, been very 
infrequently used on tunnel work and the engineer with a pro- 
ject of any magnitude in hand should make a thorough investi- 
gation of the possibilities and relative economies of this source 
of power as appHed to the particular work. At the same time 
the internal combustion engine is not adapted to work in the 
tunnel itself due to the poisonous fumes ejected and the compara- 
tively poor character of the ventilation within the tunnel itself. 

(B) Am COIMPRESSORS 

In all modern tunnel construction compressed air is entirely 
used for drilHng and pumping as well as, to a considerable extent, 
for ventilation and other mechanical operations in the tunnel. 
The reason for this is the simplicity and rugged character of the 
tools which are run by compressed air and the fact that the 
exhaust air is perfectly safe and in fact helps the ventilation. 
The choice of the proper air compressor for any particular work 
is therefore of great importance. The matter of air compressors 
is covered in Chapter V of this work. Due attention should be 
given to the difficulty of transportation of the machinery, of 
obtaining spare parts or of having repairs made, of obtaining 
labor skilled in the maintenance and operation of the type chosen, 
to securing excess capacity to take care of emergencies and of 
decreased efficiency at high altitudes. In many cases it may be 
desirable to use many small rather than fewer large units, not- 
withstanding the higher cost and loss of operating efficiency, 
and in such cases the machines should be of the identical kind, 
as this standardization simplifies maintenance and repairs. 
The average reader of this book will do well to suspend any 
decision to adopt any tyi^e of equipment that has not been 



468 MODERN TUNNELING 

thoroughly tested, with success under constant operation for long 
periods, even when such proposed equipment seems to promise 
initial economy. In tunnel work nothing is more essential 
than to keep the work going without interruption, and micro- 
scopic plant economies are of relatively small value compared 
with this feature. Remember that unsatisfactory workers can 
be discharged and others soon hired in their places, but to scrap 
or revise a plant which does not fulfill the needs, means a delay 
of weeks, as well as great expense. 

(C) Drills 

Supplementing what has been said in Chapter VIII, the 
following remarks may be added for the particular case of these 
larger tunnels. The factors which would influence the choice 
of a certain kind of drill are: the kind of motive energy, the 
quality of the rock, the size of the cross-section and the kind of 
labor available. Ordinarily at the present time some form of 
pneumatic drill would be used so that the choice narrows down, 
as a rule, to the hammer drill as compared with the piston drill. 
For driving a heading, all other things being equal, a hammer 
drill, especially when using hollow steel and flushing attach- 
ment and mounted on a horizontal bar across the heading, has 
proved itself very effective. On the other hand, the heavier 
piston drill is perhaps the better for drilling "down" holes, but 
if mounted on a tripod has disadvantages due to weight, trouble 
to set up and remove, etc. Further reference is made to this 
subject later. 

Progress in rock-tunnel construction is dependent on the 
successive operations of drilKng, blasting and mucking, and as 
the blasting and consequent smoke interrupts the other opera- 
tions it should be so planned as to reduce this interruption to a 
minimum. 

(D) Loading Equipment 

Speed in tunnel driving depends to a very large extent upon 
the rapidity with which the excavated material is removed from 
the working faces. Up to the present decade, tunnels have been 



CONSTRUCTION 



469 



almost universally mucked by 
hand labor. In a few instances, 
however, mechanical equipment 
has been tried, such as steam 
shovels (usually converted to 
air operation) loading machines 
and shovelling machines. Types 
of these latter are described in 
Chapter IX and it is perhaps 
only necessary here to say that 
these machines suffer from the 
disadvantage of occupying a 
great deal of room, w^hich often 
cannot be spared and of neces- 
sity being very heavy, they thus 
entail an elaborate track sys- 
tem. See Figures 88 and 89. 
There are material advantages 
to be obtained from the use of 
shovels fitted with flat wheels 
to operate on the floor of tun- 
nel instead of on a fixed rail- 
road track while the adaptation 
of the caterpillar drive to shov- 
elling machinery for tunnel use 
gives promise of still further 
improvement. 

The mechanically operated 
shovel is particularly adapted to 
use in bench enlargementof large 
size tunnels w^here there is ample 
space for track layout which will 
faciUtate the rail operation and 
the loading of the cars. Consid- 
erable success has been obtained 
with the adaptation of conveyor 
belts as adapted to loading. 




, — 




- 


















- 




'^ 


3" 






SECTION AT A.-A 



470 



MODERN TUNNELING 



In cases of top heading tunnels, the heading muck is almost 
invariably loaded by transferring it in small cars from the head- 
ing face to the bench enlargement where a traveUing tower, 
having a height equal to the height of the heading floor above 
the enlargement floor, operates on a rail on each side of the main 
tunnel so that it can be brought up to the face and a bridge 




Fig. 89. Power shovel in rock tunnel. 

thrown over to the heading track for loading the heading muck 
into the big main track haulage cars below, except at times when 
bench blasting is to be done, when the tower is hauled back out 
of the way. In narrow tunnels this is simphfied by using port- 
able ladders each side and forming the bridges with heavy planks. 



(E) Haulage Equipment 

Under this heading are included the cars for the spoil exca- 
vation, as well as the machinery necessary for hauling them 
within the tunnel, transporting to the surface and disposition 



CONSTRUCTION 471 

thereafter. As affecting the decision on the most advantageous 
means for removing the muck from the tunnel, there is to be 
considered definitely, in the first place, the general plan of pro- 
cedure under which the tunnel is to be built, under contract 
plans and specifications, particularly in the matter of the rela- 
tions of heading driving to bench enlargement; the question 
of whether a top or bottom heading is adopted and whether 
the enlargements are carried out in one or more benches. 

In the event that a bottom heading of large size is employed, 
then it becomes obvious that one or more substantial tracks 
can be laid on the permanent invert, and that a large size car 
can be advantageously employed, since the track will remain 
at its permanent grade right up to the face of the heading. In 
this case muck will be shot down and loaded by a power shovel 
or hand labor, at the enlargement of the main tunnel bench; 
while at the various break up points, if any, from the bottom 
heading, the muck excavated will be thrown down, through 
chutes, into cars standing on the permanent track directly below 
those points. 

In the case, however, of a top heading, then the following 
notes may be of assistance in guiding the constructor : 

(a) If the heading face is maintained at a constant and very 
short distance ahead of the bench enlargement, so that the 
blasting of the heading will throw the muck down, over the 
face of the bench, in order to be loaded on the floor level, then 
there is no necessity for the consideration of any haulage in the 
heading as separated from the enlarged tunnel; excepting in 
respect, possibly, of hand shovelling and wheel-barrows, and 
the only question remaining, in that case, is the character of 
haulage in the full size tunnel. 

(6) If the heading driving advances at a faster rate than the 
bench, so that the face of the heading is a considerable but 
variable distance ahead of the bench enlargement, then the haul- 
age in the heading would be by wheel-barrows if the distance 
is short, or by a narrow gage (21'' to 24'') light portable track, 
utiUzing a low type of dump car suitable to the track gauge, 
which can be pushed by man-power to the dumping bridge and 



472 MODERN TUNNELING 

chutes at the face of the bench; where the heading spoil is then 
loaded into the main haulage cars in the full size tunnel. If 
cars are used in this case they should be as Kght as possible so 
that derailments may be replaced as easily as possible. A port- 
able track in sections is advantageous as permitting, more readily, 
the carrying forward of the track to the shovelling plates at the 
face of the heading. 

(c) If the bench enlargement is mucked-out by hand labor 
then it is desirable to use, for the main haulage in the enlarged 
tunnel, a medium size car of a capacity of say 40 to 50 cubic feet, 
and in this case a solid non-dumping car will easily give the best 
service. If such a car as this is used, then the installation of a 
tipple at the top of the shaft, or outside the portal, is desirable 
to dump the spoil out of the tunnel car into the main line steam 
railroad dump car for hauHng to the spoil banks. Using a car 
of this type, then the main tunnel haulage can be either by wire 
rope, or pneumatic or electric locomotives, or even by mules. 

{d) In case the bench is mucked with a power shovel, then 
it is desirable to eliminate from consideration the small 2 -yard 
cars for the main haulage, and to utilize a larger size car, say 
6 to 10 yards capacity, depending upon the space available in 
the tunnel for swinging the power shovel, built as low as possible, 
of a dumping type, so that the shovel may load directly into a 
car which is suitable for hauling out over the main line for final 
disposition. In this case either a standard gage track, if the 
tunnel is large enough, or a track of ^6" gage, or thereabouts, 
will be suitable, and in that case the haulage within the main 
tunnels should be with either pneumatic or electric locomotives. 

In this case it is essential before deciding on any plan of 
haulage to lay out carefully the space available within the 
finished tunnel for the operation of the shovel and for the track- 
layout which can be utilized in connection with the operation 
of the power shovel. A power shovel is a very useless tool, 
excepting with efficient car service, upon which the shovel is 
absolutely dependent. If the tunnel to be constructed is 
small in dimension, it may be necessary to use a small-size car, 
so as to give room to the shovel to swing. If possible, it is desir- 



CONSTRUCTION 473 

able to maintain two car service tracks, one on each side of the 
shovel. In any case a system of turnouts and sidetracks immedi- 
ately in the rear of the shovel, and as close to it as possible, 
will be essential to maintain the proper feeding of the cars to 
the shovel, and the removal of loaded cars as quickly as possible. 
Usually, in tunnel work, head-room, as well as side-room, is 
very restricted, so that the cars to be used with the power shovel 
should be built as low-sided as possible to permit proper loading. 
These cars, if there is sufficient space, can be self-dumpers, or 
otherwise a large substantial sohd car which can be operated 
over a tipple at the shaft or portal to discharge into the main 
line steam railroad equipment, but, failing that, it is advan- 
tageous to use a wide fiat deck car with side pockets, allowing 
of erection of drop sides, and to discharge these cars with a rail- 
road plow at the dump. For serving the power shovel with 
car equipment, it is very convenient to have the shovel fitted 
with capstan heads or winches, to be used in pulling up empties 
to the shovel and to pull out the loads, which can be advan- 
tageously done by using fair-leads and ropes. 

In the arrangement for mucking the heading excavation 
over the bench to the main haulage in the enlarged tunnel, the 
arrangements for bridge, chutes or other dumping facilities 
should be made as flexible as possible, so as not to interfere with 
procedure with drilling and mucking on the bench heads. 

The track construction for the main haulage of the full size 
tunnel should be of a character, gage and weight of rail corre- 
sponding with the adopted equipment which the conditions of 
a particular job indicate to be most advantageous. In any case 
the main haulage track should be built substantially, well-sur- 
faced and ahgned, as a Httle money expended on the proper 
maintenance of the main haulage track will be more than repaid 
in the elimination of derailments, wrecks and other troubles, 
which are always liable to occur on construction tracks of any 
character. For the main haulage, rails should be of good weight 
and even for smaller size equipment a rail of not less than 30-lbs. 
is desired. In this track all joints should invariably be spliced 
efiiciently, and not secured by simply spiking to the ties. The 



474 



MODERN TUNNELING 



track itself with turnouts and sidings should be efficiently 
installed with proper switch levers, so that they may be kept 



S- & W c. •§ 



Fig. 90. Car dumping tipple 
used in Astoria tunnel con- 
struction. 




2-10}^- 



always in good operating condition. The cost of such small 
items as these is vastly less than the cost of delays to the power 
shovel and equipment, in turn reacting upon the entire work 



CONSTRUCTION 475 

at the face, which is sure to occur if these matters are not properly 
attended to. 

If man power loading at the bench is employed then it should 
be considered that the car body should be as low as possible to 
reduce the labor of man-handhng or shovelling. While there 
have been some instances where cars of from 40 to 80 cubic feet 
capacity were used with apparent success, it is the writer's 
opinion that for disposing of spoil from a tunnel driven with 
the ordinary heading and bench, a capacity of 40 cubic feet is 
about the largest economical size. It is better also to depend 
upon dumping the car by some separate device on the surface 
rather than by introducing any side or end dumping or tilting 
features into the car itself. These devices usually increase the 
height of the car and also its weight and complexity. It is 
beheved that equal strength is obtained with less weight with 
a wooden body, reinforced with steel bands and corners, rather 
than with an all-steel box. The former is likely to become 
worn or broken, but is easily repaired; the latter are liable to 
be deformed and are much more difficult to restore. 

It will be noted that the use of a bottom heading somewhat 
simplifies the question of car equipment or haulage. 

After the description of haulage methods in Chapter IX 
very Uttle remains to be said. It may be well in passing to 
point out that the delay and loss of time in extending the cable 
system is of less importance when the work is so organized that 
this extension may be made between shifts or during week ends. 
Further, attention is called to the fact that electric locomotives 
of the trolley type are not suitable for bottom heading methods 
of excavation. 

In the matter of dumping at the surface it may be noted 
that this is usually done by means of derricks or by tipples. One 
of the latter which gave entire satisfaction is shown in Figure 90. 

(F) Drainage and Pumping 
As tunnels are seldom planned with level grades and as they 
are usually driven from opposite ends, water, if present, will col- 
lect near one working face, whence it must be pumped to the 



476 MODERN TUNNELING 

open. For this purpose a rugged simple pump, capable of hand- 
ling dirty water, should be considered when there is the requisite 
steam or air supply available. These pumps have to be moved 
along, from time to time, as the work of the heading and bench 
advances, the discharge mains being extended at the same time. 
On the suction end the foot valve is usually connected with the 
pump by a long length of flexible hose which can be withdrawn 
to avoid injury by blasting. If centrifugal pumps, driven as 
above or by electricity, are used, care should be taken to see 
that a sand pump and not a water pump is selected. One great 
disadvantage in the use of electrically driven pumping plant for 
down grade tunnels is that there is danger of the tunnel becoming 
flooded by interruption of the power supply or motor trouble, 
and if this should occur, the motor would be ruined. It is neces- 
sary in such cases to make arrangements for pulling such pumps 
out of the tunnel on short notice. This also shows the further 
desirabihty of having dupHcate pumping equipment on hand. 
On the other hand a compressed air pump will usually start 
even when completely submerged. An inexperienced engineer 
who may be laying out his pumping system largely by copying 
some previous example, is warned that proper consideration 
should be given to the avoidance of sharp bends; the provision 
of ample diameter of pipe, and to full allowance for the friction 
head developed on discharge lines of long length. For tunnels 
where the flow of water is naturally away from the face, nothing 
but ditches are required. Where the flow is very large, it may 
be necessary to raise the track system high enough above the 
bottom of the tunnel, so that the entire width of the tunnel acts 
as the ditch during the construction period. 

(G) Ventilation 
The ventilation of tunnels under construction is one of the most 
important things that can be considered by the engineer. Not 
only is a badly ventilated tunnel an act of inhumanity but from 
the point of view of dollars and cents alone it is most short-sighted 
not to keep the air in the working space in a healthful condition 
for the workers. When the face of a rock tunnel is fired the 



CONSTRUCTION 477 

workings become- filled with dense smoke, gas and dust, and until 
this clears so that men can see and breathe freely, the work is at 
a standstill. The only way to cut down this loss of time is to 
exhaust the foul air or to blow in fresh, or both. Probably the 
most usual arrangement is to blow the air into the tunnel through 
ducts laid for that purpose and which terminate near the working 
face. The practical details of proportioning a ventilating sys- 
tem are described in Chapter VI and it is only necessary to say 
here that in very long tunnels under construction, it may be 
necessary to introduce additional blowers (Boosters) on the 
main Hne, where the size of the ventilating pipe has been kept so 
small that the fan at the portal cannot force the air to the face. 
Intermediate blowers may also be required for subsidiary work- 
ing points, for example, at places where lining work is in progress. 
It has lately been emphasized in industry that good ventilation 
and Hghting are prime factors in increasing output and this is 
also true in tunnel work. 

The use of an auxiliary tunnel for access and ventilation at 
Rogers Pass or "Connaught" Tunnel, in Canada hereinafter 
referred to, is a solution of many difficulties in very long tunnels, 
but such a system must be studied on its own merits in relation 
to the particular job under consideration. 

(H) Lighting 

The same thing applies to lighting as to ventilation, namely, 
that good light is essential to good progress. The days of 
candles are fortunately past, as far as railroad tunnels are con- 
cerned, and the only methods of lighting that need be discussed 
here are electricity and acetylene gas. As to the former, the 
ordinary incandescent lamp will be used for the general hghting 
through the tunnel, but a good word should be said for the arc 
Hght at points where actual work is in progress. This type of 
Hght hterally turns night into day and is of great help in securing 
speed and good quality of work. Probably, moreover, actual 
economy in current consumption for the same degree of Hght is 
obtained by their use. 

For the general illumination by incandescent lam.ps it is 



478 MODERN TUNNELING 

necessary to use lamps with anchored filaments which will stand 
the rough handling incident to tunnel construction. In tunnels 
which are subject to flooding to the extent of possible danger of 
forcing men to flee for their lives, it is good policy to keep lighted 
oil lanterns hung at intervals through the workings to provide 
against the possible failure of the electric lighting system, in 
such an emergency. The acetylene lamp is the only rival to 
electric lighting, and has the advantage that no plant or conduc- 
tors are needed. It is self contained and can be moved wherever 
needed. It is now provided in large units for general illumination 
and has an advantage that a man can carry an individual lamp 
for local use wherever he may be although the care of these lamps 
is apt to be troublesome, an excuse for loafing and the loss and 
breakage is large. For any work of sufficient magnitude to war- 
rant the use of compressed air for various purposes, there seems 
on reason for not installing sufficient electrical apparatus to give 
adequate lighting in the tunnel. It can only be because of the 
habit formed by custom that any tunnels driven in recent years 
have not been well Kghted. A Hberal provision of illumination 
is a most important factor in the reduction of personal injury 
and in the promotion of the safety of employees and the work, so 
that, if for no other reason, the expense is amply warranted by 
resultant economy. 

(I) Surface Equipment 

This will vary to some extent, depending upon whether the 
work is conducted from shafts or portals. In the former case 
part of the surface equipment will consist of winding gear to 
raise and lower materials. It is usually found economical to 
install regular elevators or ''cages" for this purpose — after lining 
the shaft, if this is desired, rather than to rely on the cruder 
forms, such as a derrick, which is necessary during the shaft 
sinking operation, and which for the tunnel operations would be 
not only slower but unsafe. Even with a portal, hoisting arrange- 
ments of some kind may be needed as when the spoil has to be 
removed by wagons or loaded into a crusher. Unless the local 
conditions permit immediate disposal into a spoil bank, the use 




of surface plants ^ York 



[Face page 479] 




Fig. 91. Ari-angement of surface plants for the 



the North River tunnels of the Pennsylvania Railroad at New York 



CONSTRUCTION 479 

of a locomotive crane is a very valuable means of assisting in 
disposal at the surface. 

One of the essentials in tunnel excavation is to empty the 
muck cars as quickly and cheaply as possible and to keep the 
cars in active operating use. 

In general the topography adjacent to the portal or shaft, 
the requirements of fills for the line, if any, whether or not any 
rock is to be set aside for crushing for concrete or for rock pack- 
ing and similar considerations, govern largely the selection of 
the most desirable surface layout. 

Other items of plant which will be located and operated 
entirely on the surface are the blacksmith shop, which for a 
tunnel of any magnitude, must certainly be equipped with a 
mechanical drill sharpener in addition to the ordinary forges; 
the machine shop for lathes, shapers, drill press, bolt and pipe- 
threading machines, saws and other equipment to whatever 
extent the local conditions may require; the carpenter shop, 
which should be equipped with the more generally used kinds 
of mechanical tools, such as rip saw, swing saw and band saws, 
planing machines, pneumatic augers, etc., so that expensive 
hand carpenter work may be minimized. 

Provision must be made for the concrete mixing plant if the 
tunnel is to be hned with that material, cement sheds, storage 
piles for sand and stone, storerooms, etc. Figure 91. 

(J) Camp 

Too much emphasis cannot be placed on the importance to 
the conduct of an important tunnel enterprise, of a practical 
and thorough study of the camp layout and equipment at each 
working point. In remote localities where the men employed 
have to be provided with Uving accommodations at the site of the 
work, camps will have to be built and maintained. It may be 
set down as a general principle that the better the faciUties 
furnished the better will be the work done, the less the turn- 
over of labor, and the greater the ultimate resulting economy. 
In some places the minimum requirements from the stand- 



480 MODERN TUNNELING 

point of general well being, are prescribed by law; but it must 
be kept in mind that such requirements are minimum and not 
in all cases a desirable standard. In general, the least a 
competent and self-respecting workman is entitled to expect is 
that he will not be compelled to share a sleeping compartment 
with more than one other. An ideal worth striving for is indi- 
vidual sleeping quarters. Since the World War the living 
standards of all classes of workmen have advanced and as there 
bids fair to be no great surplus of labor, at least of the kind here 
discussed, for some time, the reader is warned against arranging 
for the very crude living conditions which have been associated 
generally with construction work in the past. As to living 
quarters, the method of construction, the arrangement of houses, 
the size of the camp, whether or not provision is to be made for 
wives and children, with schools for the latter, recreation build- 
ings, etc., depends upon the location of the work, its size, the 
duration of the construction period and to the kind of labor 
employed. Speaking generally, running a camp is apt to be a 
vexatious problem. For this reason, while it is felt that the 
engineer or superintendent should have full jurisdiction over all 
camp matters, it is best that he does not attempt to take direct 
charge of it, as there are many petty problems that cannot get 
adequate attention from an otherwise busy man. The better 
plan is to chose a camp foreman, selected for his tact and firm- 
ness, put him in sole charge and hold him responsible for results. 
If there is a medical officer the camp foreman should be made to 
cooperate with him. An essential feature for the support of the 
conscientious, capable camp foreman is the hearty backing of 
his superior. The question of farming out the commissary is 
one about which a good deal of hesitation may well be used. 
The feeding of a large number of men in an isolated district is 
naturally a troublesome matter but if done well, warrants the 
trouble. It is probably a truism to say that a well-fed man does 
the best work and is most contented, and the converse is also 
true — that a badly fed man will not give his best services. It 
will pay an organization to look in any other direction than the 
commissary to make supposed economies. With the exception 



CONSTRUCTION 481 

of married men, no workers should be allowed to prepare their 
own food, as the result is inevitably poor. 

Nothing more can be said here about field offices other than 
to point out that too often the tendency is to construct poorly 
built, inadequately furnished and feebly heated shacks in which 
the engineering and construction forces have to work, under such 
conditions that their efficiency is impaired. Every project of 
any size warrants the construction of decently built and equipped 
offices. In addition no camp should be without steam-heated 
drying rooms and locker equipment should be provided so that 
men coming wet out of the tunnels may change their clothing, 
besides which there should be covered ways between top of 
shaft and drying rooms, if the work is carried on at high alti- 
tude or in cold climates. 

In these days the study of social and industrial welfare work 
has become a definite branch of science. As appHed to certain 
camp equipment for tunnel work, it can be considered of vital 
importance to efficient service and consequently to the progress 
and economic results of the work. Tunnel work, to the workers, 
is at all times hazardous, most of the work is carried on in the 
dark or under artificial fight and often in wet conditions and 
some times at high temperatures, all of which tend to sap the 
vitahty of the worker. If added to this, the work is in a remote 
locality, away from any town or community, it can be readily 
understood why, in former years, the saloon established, just 
beyond the limits of camp, often by local politicians, was such a 
thriving source of revenue to the promoters and such a source 
of demoralization to the working forces of the contractor. The 
addition to any such camp of a hall and provision for definite 
programme of amusements will be of immense service in main- 
taining the morale of the organization and will in reality, 
increase efiiciency and promote economy. 



CHAPTER XX 

HARD ROCK TUNNELS 

(Self-supporting) 

EXCAVATION METHODS 

One essential difference between the tunnels described in 
Chapter XI and those to be now considered, is that in the exca- 
vation of the former, the rock was taken out to the full cross- 
section of the tunnel at one operation, whereas in railroad and 
other tunnels of large cross-section it is almost universal to carry- 
on the excavation in two or more stages, the arrangement of 
which will depend upon the size and shape of the cross-section 
of the tunnel, the nature of the rock and other local conditions. 

If a railroad tunnel were excavated with the full cross-section 
in one plane, it would mean that all the rock would have to be 
blasted with only one free face, which would require the expen- 
diture of much drilling and explosives. In addition the work 
of drilHng would be awkward and expensive, as scaffolding would 
be required to reach all points of the face, with many conse- 
quent disadvantages. Hence methods have been developed 
whereby only a small portion of the full cross-section is first 
driven. This is called the ''heading." After the heading has 
advanced a sufficient distance to permit separate operations of 
drilHng, blasting and mucking, to prosecute work behind with- 
out interfering with work at the face, a gang is started at the 
task of enlarging the heading to the full cross-section. It will 
be seen that the driving of the heading has resulted in giving 
the rock to be removed in this enlargement, one other free face 
and has provided the further advantage of permitting a larger 
number of men to work at the drilling without interfering with 
each other and to reach and attack their work without any 
scaffolding. 

The advance heading may be placed in any part of the full 

482 



HARD ROCK TUNNELS 483 

cross-section. It has been and still is the usual practice in this 
country to place the heading at the top. The width of this top 
heading may or may not be the full width of the tunnel. Sup- 
posing for the moment that the heading is at the top and for the 
full width of the tunnel, which is the simplest cast, the next 
stage is to excavate the remainder of the cross-section, which is 
known as the ''bench." In some cases even, as will be seen, this 
latter may in turn be removed in two stages. In the less gen- 
eral case, where the heading has been driven for the full width 
and is located at the bottom of the cross-section, the remainder 
or upper portion of the cross-section will be removed by drilling 
upward from the roof of the heading. Again, there have been 
instances where, what has approximated a full width heading, 
has been driven in or near the middle of the cross-section, with 
subsequent enlargement of the top and bottom, which are, how- 
ever, not conveniently done simultaneously. Finally, there has 
been a conspicuously successful example of a small central 
heading from which radial holes were drilled to enlarge to the 
full cross-section. This is summarized later on. 

While the practical tunnel man in this country will naturally 
lean to a top heading, the engineer nevertheless is cautioned not 
to follow bhndly any precedent, however general, until he has 
satisfied himself, by a comprehensive study in his particular 
case, that the proposed method of driving best fulfills the follow- 
ing requirements: rapid progress, low unit cost and safety during 
construction. 

The chief factors which will give these results are: reduction 
of drilling and explosives to a minimum, especially in the head- 
ing, ease of removal of water, facihty for ventilation, working 
the maximum number of men at any one time that can be effi- 
ciently employed without mutual interference, the reduction of 
the slow and expensive heading work to as small a proportion 
of the cross-section as is possible, consistent with obtaining the 
other advantages which a heading gives, planning the work, 
both drilling and mucking, that wherever possible the work goes 
with the force of gravity rather than against it, and the simpli- 
fication of the transportation of the spoil. 



484 MODERN TUNNELING 

In the consideration of the relative merits of top or bottom 
headings in connection with a railroad tunnel in rock, it should 
always be borne in mind, if there is the probability of finding 
as the work advances that the roof is bad and heavy, that then 
a top heading will be of great advantage in enabhng proper sup- 
port of the roof and consequently faciHtate the prosecution of 
the work; in which case the selection of a top heading would be 
amply warranted as against other objections. On the other 
hand in soft ground mining with timbering methods, the selec- 
tion of bottom headings to give permanent foundation to main 
posts and side wall lining is much to be preferred, as the later 
removal of the arch is greatly simpHfied and enlargement is 
safer if the foundations are first secured. 

Railroad tunnels of the length discussed in this book are 
generally driven from the two portals, without the use of any 
intermediate shaft or adits. Nevertheless, as the speed of driv- 
ing depends upon the number of points of attack, the possibilities 
of multiplying the number of headings by means of a shaft or 
adit should be carefully examined. 

SIZE OF HEADING 

The size of the heading should be governed primarily by the 
fact that what is sought is speed of driving it. This means that 
considerations as to the method of drilling the heading, as for 
example, vertical columns versus horizontal bar mountings, 
shallow versus deep holes, the quality of the rock, character of 
temporary and permanent lining, etc., all will influence the 
width of heading adopted. Whatever the width, however, the 
height should be sufficient for men to stand erect comfortably. 

In order to enlarge the remainder of the cross-section with 
the most economy, the size of heading should be planned to 
permit of the subsequent enlargement drilling to be done as 
cheaply as possible. 

There are endless varieties and combinations of the three 
main methods, viz., top, bottom and center headings — which 
have been used. The cross-section of the tunnel may be so 
large (as for instance in a double-track tunnel) , that two advance 



HARD ROCK TUNNELS 485 

headings at the sides may be necessary to excavate rapidly and 
economically. It will be seen that this arrangement enables 
the number of men engaged to be doubled, both as regards the 
driving and subsequent enlargement. In each case, careful 
consideration and experimentation should be given to determine 
the best location and size of the advance heading or headings. 
It should be stated here, however, that in homogenous rock, the 
size alone of the heading having been decided on, whether or 
not it is to be placed in one or another part of the full cross-sec- 
tion will depend upon the advantages or disadvantages which it 
offers to the removal of the remainder of the cross-section. The 
pages w^hich follow contain points on drilling, blasting and muck- 
ing which bear on the choice of top, or bottom heading. Further- 
more considerations of drainage may have a large part in deter- 
mining the location of the heading, bottom headings being useful 
in draining large flows of water. In the case of very wide tunnels 
in variable rock, two side headings have the advantage of dis- 
closing in advance the nature of the material that will be 
encountered over the full cross-section. 

The heading affords a void space into which to break the rock 
in the enlargement, whereas the excavation of the heading itself 
involves the penetration of the virgin rock As may be sup- 
posed, the cost per unit of volume of excavation is higher in the 
heading than the cost of the same volume in the enlargement. 
In order, therefore, to keep the general average cost of the 
total excavation to a minimum, it may be necessary to keep 
the cross-section of the heading as small as possible. There 
are certain limitations imposed by the fact that the heading 
must be large enough to work in. Therefore, it should be high 
enough for men to stand upright, allowing sufficiently for the 
possible necessity for temporary timber to support the roof. 
This would indicate therefore a clear height of not less than 
7 feet. It must be wide enough so that the drills can be mounted 
to give the proper inclination to the holes to take out the cut, 
which will usually be the ^'V" or ''wedge" type described in 
Chapter XI, and it must be large enough so that the muck cars 
can be run into the heading and loaded without cramping the 



486 



MODERN TUNNELING 



men. The most usual widths used vary from a minimum of 
6 feet to the full width of heading at the heading floor grade. 

COMPARATIVE COST OF TUNNEL EXCAVATION IN TRAP ROCK. 
YEARS 1906 AND 1907 



liem 



Headings 



Enlargement 



Whole Work 



Superintendence 

Plant running 

Drilling and blasting 

Explosives 

Timbering 

Mucking 

Disposal 

Lighting 

Ventilation 

Freight 

Insurance 

Interest 

Dismantling plant . . . 
Miscellaneous 



So. 30 
1-55 
5-23 
1. 00 

1.20 

2.48 
0.30 

O.OI 

0.02 
0.42 

O. 12 
0.44 



So. 12 
0.78 
2.24 
0.29 
0.03 
0.76 
0.63 
0.15 
0.02 

O.OI 

0.22 

0.03 
0.47 



?0.24 

1.07 
2.83 
0.43 

1.05 
1.09 
0.18 

O.OI 
O.OI 

0.23 
0.03 
0.47 



Total cost per cubic yard 



|i3-07 



$5-75 



$7-64 



In this case the current rates of wages were : 

Drill runner S3 • 50 per day 

Drill helper 2 . 00 per day 

Heading foreman 5 . 00 per day 

Walking boss 7 . 50 per day 

Many factors enter into each specific case presented and no 
two cases are alike. So much depends on the degree of hard- 
ness of the rock, the way it breaks, the lie of the strata, the 
amount of water present, whether the tunnel is down grade so 
that the water flows to the face or up grade so that it flows away, 
the degree of skill and experience of the superintendence and 
of the labor, the type of drills used, the grade of powder and so 
on, that the only proper guide is experience and experiment. 
In certain cases, within the author's experience, it has been 
found that, instead of a small heading being the most economical 
a large heading reaching across the entire width of the finished 



HARD ROCK TUNNELS 



487 



tunnel section may give better results. One thing should be 
remembered and that is that the controlling economy in most 
tunnels is speed of advance. The more feet of tunnel that can 
be driven in a unit period the cheaper the work will be. As the 
speed of advance of the heading controls the speed of advance 
of the enlargement, usually that section of heading which will 
admit of the greatest speed of advance will be the most economi- 
cal section. To show, in a general way, and as illustrations 
only, the difference in cost between driving a heading and 
enlarging to full cross-section, the preceding figures are given. 
The first figures are obtained from the construction of the 
Bergen Hill tunnels of the Pennsylvania Railroad through the 
trap rock of the Palisade ridge at Weehawken, N. J. and repre- 
sent the cost to the contractor only. 

The average advance made in the heading per 24 hours was 
5 feet. The depth of the holes was 10 feet, the diameter of the 
holes 2f inches, the depth of hole drilled per drill per hour was 
2.7 feet, the depth of hole drilled per cubic yard was 50 feet. 
The dynamite used per cubic yard was from 3.4 to 5.7 pounds. 

The following figures have been taken from the records of 
the Astoria Gas Tunnel driven in the years 1911-1912 through 
gneiss and dolomitic limestone under the East River at New 
York. 





Average per Actual Cubic Yard 


Item 


Gneiss 


Dolomitic Limestone 




Heading 


Bench 


Total 


Heading 


Bench 


Tocal 


Drilling, in feet 

Pounds of dynamite 60 % 

No. of exploders 


564 
4.20 
0.79 


304 
1-35 
0.38 


4.22 
2.65 
0.57 


5 09 
4-35 

0.71 


2.03 
1.08 
0.26 


3 42 
2.57 
0.46 



This is another striking confirmation of the high cost of 
heading work as compared with that of the enlargement. The 
amount of drilling required in the heading is roughly double 



488 



N TUNNELING 



that in the bench. The amount of explosive is about 3! times 
as great. 

The general actual cost of tunnel driving on this work, 
including all operations, in the gneiss and dolomite together 
was as follows: 



item 



Cosu per Actual 
Cubic Yard 



Per cent of Total Cost 



General supervision 

Field engineering 

Field administration 

Plant and equipment 

General labor and supplies 
Contingencies 



Drilling 

Blasting 

Timbering 

Mucking 

Disposal 

Power and plant running. 
Drill sharpening, labor . . . 

Lighting 

Extending lines 

Pumping 



Total 



I0.078 
0135 
0.563 
0.846 
0.293 
0.690 



0.861 
1.003 
0.003 
1.462 

1-379 
0.807 
0.258 

0.154 
o. 141 

0.133 



$8 . 806 



0.90 

1-53 
6.40 
9.61 
330 
7 . 83 Tot. indirect 29.57 



9.80 
11.38 

0.03 
16.60 
15 63 

9.18 

2.93 
1.76 
1.60 
1 . 52 Total direct 70.43 



[OO.OO 



100.00 



The current rates of labor paid on this work were 

Superintendent $250.00 per month 

Assistant superintendent . . 

Heading foreman 

Bench foreman. 

Drillers 

Drillers helpers 

Muck boss 

Muckers 

Pipe fitters 

Pipe-fitters' helper 



200 . 00 
5 . 00 per 8-hour shift 
4-50 
3-50 
2.50 
3-50 
2.00 
3.00 
2.50 



The cost of the 60 per cent ^'Forcite" dynamite used was 
12.30 cents per pound. The cost of drill steel averaged $0,067 
per pound. 



HARD ROCK TUNNFXS 

All these costs of labor and materials would be increased two 
or three times at the present day. In the city of New York at 
the present day the lowest rate of labor in tunnels under normal 
air pressure is $6 per 8-hour shift. This tunnel had a theoreti- 
cal cross-sectional area of 331.76 square feet or 12.29 cubic 
yards per Hnear foot. There was actually an overbreakage of 
17.9 per cent over the net cross-section so that instead of 12.29 
cubic yards excavated per foot there was taken out some 14.52 
cubic yards. The overbreakage in the heading was 22.6 per 
cent and in the bench 14.3 per cent. The entire work was con- 
ducted from the two terminal shafts, one on each side of the 
waterway and 4662 feet apart. The shaft on one side was 277 
feet deep and on the other 242 feet deep. The strike of the rock 
cut the course of the tunnel at an angle of some 2 2§ degrees and 
the dip of the strata was close to being vertical. 

It is perhaps worth emphasizing that these detailed figures 
are given as merely illustrative of the results obtained under 
certain conditions and are in no sense to be taken as a guide or 
index for any other case which may be presented. The only 
way to make a proper estimate of the cost of a proposed piece 
of work, and the way which an experienced contractor would 
follow in making a bid, is to consider the local conditions under 
which the work will be performed to conform to the contract 
specifications, the governing wage rates, the material prices 
and the size and character of the tunnel. To estimate the 
complete staff and force required to carry out the work, the plant 
required, the haulage expense, the camp expense (if any), 
the transportation, the charges for insurance and guarantee 
bonds and the financing, and thus to arrive at a total monthly 
expense. Then to estimate the probable monthly progress, 
which will give the duration of the job, and thus arrive at a 
probable total actual net cost. To this has to be added an 
allowance for contingencies and profit. 

To use previous prices at which other work has been per- 
formed in the past, under unknown or different conditions of 
locality, rock, climate or date, may be, not only misleading but 
positively dangerous. 



490 



MODEHN TUNNELING 



It is worth noting that the costs of excavation given in the 
foregoing illustrations do not by any means represent the same 
costs at each heading on the same work but are average costs 
of the various points of attack. It is almost invariably the 
case, that there is a material difference in actual cost, whether 
of heading or enlargement excavation, between the opposing 
ends or even between two parallel tunnels executed at the same 
time and under the same conditions and general direction. 
These differences are due in part to the personal factors but also 
to variations in working conditions. 



In the 
been 




DRILL MOUNTING 

eastern states, at least, the method of drill mounting 
almost always by column (Figure 92) and not by 
horizontal bar (Figure 93). In many 
cases, no doubt, this is a result of con- 
servatism rather than of analysis and may 
be attributed in part to a lack of knowl- 
edge of the advantages of the horizontal 
bar mounting. In other cases, where a 
wide tunnel has been driven with a full 
width heading, a bar was not feasible. 
Where the upper part of a tunnel is a 
half circle and is taken out as a top 
heading in one operation the shape of 
the section is ill adapted to the support 
of a bar. 

Very considerable success was obtained 
in the Loetschberg tunnel with a travel- 
ling drill carriage in the advance bottom 
heading.* This consisted of a carriage 
on wheels running on rails laid each side 
of the heading and mounting a long mas- 
s-ively built arm carrying at the extreme 
end an adjustable arrangement of drill 



Fig. 92. Drill Column. 



* Engineering News, December 31, 1908. 



HARD ROCK TUNNELS 



491 



bars with drills attached in position for commencing next round 
of driUing. The function was to save time in drill set up at 
the face after shooting a round. The modus operandi is to 
withdraw out of danger the drill carriage before blasting a 
round. The blast piles up debris for some distance back from 
the face. Consequently the carriage is advanced so that the 
arm carrying drills reaches over the pile of muck and as soon 
as the air is clear enough for drill runners to work, the drills 




Fig. 93. Horizontal bar for drill mounting. 



are in position without waiting for mucking to clear space for 
the new set up. The carriage is designed so as not to inter- 
fere with mucking operations. Figure 94. 

In most railway or other large tunnels, the ''V" cut is the 
one commonly used in the heading. The depths of holes and 
their location is determined largely by the fact that in such 
tunnels the work is arranged, if possible, on the basis of three 
8-hour shifts per day. As it is desirable for the work of each 
shift to include a complete cycle of setting up, drilling and firing, 
the depth of holes is influenced by this factor. In common 



492 



MODERN TUNNELING 




o 



HARD ROCK TUNNELS 



493 



with the smaller sized tunnels discussed in the earHer portion 
of the book it is believed that three shifts is the most economical 
method of work on railroad tunnel driving With this arrange- 



• • • 


• • • 11 




















i 




Fig. 95. Arrangement of drill holes suited to a single 
track railroad tunnel in sound hard rock. 



ment in mind, the character of the rock will 
be next in importance in determining the 
size, depth, location and number of holes in 
the heading. It seems necessary to repeat 
here, that in a tunnel of some length, no fixed 
program of drilling should be settled without 
carefully conducted and thoroughly analyzed 
tests being made, to find a basis for the best 
method. To guide the reader. Figures 95, 
96 and 97 show typical drilling methods in 
various railroad tunnels. 

For railroad tunnels, the use of electric 
firing is advocated for blasting, especially for 
the cut. Since only three rounds are fired, 
there will be only three periods of delay to the 
work caused by the necessity for waiting for 
the smoke and gases to disappear ; and except in unusual cir- 
cumstances, the drilling progress is such that ample time is 
provided for these delays, especially where the drillers are 
permitted to knock off when they have done their task. In 
the relievers and trimming holes, it is of less importance to use 
electric firing, but usually it will prove to be better and more 
convenient to do so. 



494 



MODERN TUNNELING 



If a top or bottom heading, for any reason, has not been 
excavated to the full width of the tunnel, steps should be taken 
to do this as soon as the face of the heading is far enough 
advanced to permit of this being done without interference with 
the driving of the advanced heading. Since the rock to be 



/ * ■ 

/ • • • 

'• • • 


• • •^ 
• • • • 


1 


1 



Hammer Cut Top Heading 




Fig. 96. Arrangement of drill holes suited to a single 
track railroad tunnel in moderately hard, seamy rock. 



removed has two free faces, the point of attack 
usually will be along the side of the heading, 
rather than along the bottom ; and the amount 
to be removed at one lift is best found from 
trial. It is to be noted that the blasting of 
such enlargements will take place simultaneously 
with the main heading. Since the speed of 
tunnel driving is dependent primarily on the 
speed of heading progress, none of these sub- 
sidiary operations must be allowed to interfere 
with that work. 

After a top heading has been removed to 
the full width, the remaining portion of the 
cross-section, or the bench, will next be 
attacked. This is usually done one lift at a time, by a row of 
holes drilled along the floor of the heading, parallel to the verti- 
cal or free face of the bench. It is often advantageous to assist 
the previously mentioned holes, by drilhng what are known as 
'' lifters " horizontally in from the foot of the bench. In some 
cases only the former kind, and in very infrequent instances 
only the latter kind, of holes are found necessary. 



HARD ROCK TUNNELS 



495 



Up to recently, bench holes, whether vertical or horizontal, 
have usually been drilled from tripod mounts. Figure 98. The 




Top Heading by Side Drifting for Wall Plates 



U 



^:^ 



Fig. 97. Arrangement of drill holes suited to a single 
track railroad tunnel in soft rock or hard clay 
requiring timbering for temporary support. 

recent development of the air hammer drill, 
held in the hand, the efhcacy of which was so 
clearly demonstrated in shaft sinking, is tend- 
ing to supplant the tripod mounting. Tri- 
pods are cumbersome to carry from and to 
the point of work before and after blasting, 
awkward to set up, not particularly well 
adapted for lifters or side holes because of 
the necessity for clearance; and any other 
type of drill which obviates these disadvan- 
tages, as does the jack hammer, is obviously 
an improvement. Again, the tripod mount- 
ing shows to best advantage on holes of large 
diameter and depth, and usually bench drilling 
can be so planned as to substitute for these 
shallower and if necessary smaller diameter 
holes. Hand drills require less skill to operate, 
use less air and probably unconsciously result 
in reducing the amount of explosives used, as they use, in 
general, steel of a smaller diameter than the mounted drills. 
They are, however, better adapted to the softer rocks than to 
the extremely hard rocks, such as trap or granite which need 
more piston diameter and power to effect efficient drilling. 



• 
• 


L _J 

• • 

• • 


• 
• 


• 
• 


• • 

• • 


• 
• 









496 



MODERN TUNNELING 



Of almost equal importance with the drilling and blasting is 
the question of the disposal of the blasted material. This has a 
great effect on the speed of tunnel driving, as no advance can be 
made if the workings are encumbered by heaps of muck. Since 
the speed of driving a tunnel is dependent upon the speed of 
driving the heading a primary requisite in the cycle of operations 




Fig. 98, Tripod for drill mounting. 

is to get the blasted rock out of the heading so that the drills may 
be set to work on the next round. 

In some cases, particularly where the rock is likeily to weather 
and falls or disintegration of the roof are to be expected, so that 
the roof may have to be timbered as the heading proceeds; the 
plan is adopted of maintaining rigid and exact relation of the 
heading face, at a few feet only in advance of the bench. The 
obvious advantage of this, with a full width top heading, is that 
the muck from shooting the heading is blasted clear down over 
the bench and can be removed by the power shovel. (Cf. 
Liberty Tunnel, page 536.) The disadvantage is that the prog- 
ress must be set by the slower advance whether of heading 
or bench, and the operations at heading and bench must be 
considered as interlocked rather than as two operations proceed- 
ing independently. 



HARD ROCK TUNNELS 497 

The different appliances for mucking have been described 
in this Chapter and in Chapter IX. It is only necessary here 
to consider mucking methods as affected by the cognate sub- 
jects of sequence of excavation, drilling and blasting. 

Top or Bottom Heading 

In the top heading method, which is the more general, the 
drillers will usually shovel the rock only far enough back from 
the face to permit them to set up their columns and the muckers 
will attack the pile from the back end, load it into wheel barrows 
or small-size hand cars and work back to the bench face over 
a plank runway, supported on a travelling tower or from ladders 
set up each side of tunnel, extending back behind the face of 
the bench, from which the barrows can be dumped, direct or 
through chutes, into cars standing on the construction track 
on the floor of the completely excavated tunnel. It will be 
seen from this that the distance between the heading and the 
face of the bench should be at least enough to permit the sepa- 
rate drilling gangs to work without interference but not any 
greater, as this would mean unnecessary wheeHng of the heading 
muck. It is, of course, desirable to place and charge the holes 
drilled, so that the amount of drilHng and explosives will be a 
minimum and the length of advance a maximum. These advan- 
tages should not be gained at the expense of breaking the rock 
in a manner which leaves it heaped against the face or in chunks 
so large that they are not easily handled. Blasting of heading 
should be heavy enough to shoot the rock well away from the 
face. It appears that the tendency in this country is to use too 
httle powder. The shooting and mucking of the bench proceeds 
simultaneously with the same operations in the heading and the 
mucking of the bench is carried on below and to the sides of the 
overhead bridge platform previously mentioned. It is obvi- 
ously an advantage to keep the head end of the construction 
track as close to the bench as is possible. See Figure 99. cf. p. 536. 

Although the top heading has been used almost to the exclu- 
sion of the bottom heading in this country, it must not be taken 
for granted that the latter has not several important advantages, 



498 



MODERN TUNNELING 



the chief being that it takes advantage of the force of gravity 
in a way not possible with the top heading. After driving a 
bottom heading the remainder of the section can be broken 
down by s toping, and the broken rock allowed to fall into the 
cars through openings in movable timber platforms, provided 
for that purpose. This means that the work of mucking of at 



J' 




Fig. 99. Removable scaffold for mucking heading. 

New York. 



Astoria gas tunnel, 



least 50 per cent, of the section is greatly reduced. In the top 
heading method any decrease in the progress of the bench is 
liable to slow down the heading driving. With the bottom 
heading on the contrary, if the enlargement work falls behind, 
new upraises can be started at any convenient places, and fresh 
points of attack thereby opened up. In the meantime the prog- 
ress of the heading is quite unaffected, as the heading muck, 
by this method, is not wheeled but shovelled directly into cars 



HARD ROCK TUNNELS 499 

at the face. In timber tunnels, the bottom heading has still 
further advantages, as will be shown further on. as the timber 
is built from the bottom up and has secure foundation and, 
once in place, is in less danger of being shot down. 

Center Heading 

The most striking example of the center heading method of 
tunneling is the Rogers Pass Tunnel, on the Canadian Pacific 
Railway through the Selkirk range in British Columbia. 

As the American records for hard rock tunnel dri\dng were 
achieved here by employing unusual methods and so far as can 
be learned without sacrificing economy, this work will be con- 
sidered in some detail. In addition the reader is urged to read 
the paper on this work, reference to which is made in the bibli- 
ography. 

It is slightly more than 5 miles long, and with the exception 
of 1200 feet and 400 feet respectively of soft ground at the east 
and west portals, it is driven through what the Canadian Gov- 
ernment geologists have called quartzite. The tunnel is double 
track and the line of excavation is 26 feet 6 inches wide, the upper 
part a semicircle of 13 feet 3 inches radius and the height at 
center line 21 feet 9 inches. (Figure 100.) 

Another feature connected with this tunnel is the use of a 
separate small and distinct timnel located some distance from 
and parallel to the main turmel and which is driven in advance 
of the latter. The purpose of this auxiHary or pioneer tunnel as 
it is called, will be understood from a survey of the general prob- 
lem of driving this tunnel. (See Figure loi.) 

It must be understood at the outset that the rapid comple- 
tion of the main tunnel was deemed essential by the railway com- 
pany. The logical procedure was to drive from as many points 
as could be secured in addition to the two portals. Shafts and 
adits were found impracticable. Recourse was then had to the 
system which had been used in Europe, namely, the driving of a 
small heading parallel to the main line and distant from it, in 
this case 50 feet; then to branch off from this small tunnel with 
cross drifts driven to intersect the main tunnel. This would 



500 



MODERN TUNNELING 



H— .- 



ROGERS PASS TUNNEL 

HALF SECTION OF MAIN TUNNEL 

AND CENTER HEADING, SHOWING COLUMN 

AND DRILL SETTING, FOR RING DRILLING 



Note: Columns and Arms 101)6 set as 

Bhown, by measurements from 

Engineer's Lines. Each hole to 

■•. Ije pointed by using Clinometer 

s Board, and length of Steel shown 

\ to be fully run out. 




Fig. ioo. Rogers Pass tunnel. Cross-section and arrangement of center 
heading and drill holes. 



HARD ROCK TUNNELS 



501 







^ 



502 MODERN TUNNELING 

permit a pair of headings of the main tunnel to be started at 
each cross drift. 

Such a pioneer tunnel not only speeded up the time of driv- 
ing the main tunnel by providing more headings, but the officers 
of the railway company claim the following advantages which 
appear to have been proved.* 

■ I. The ventilation of the tunnel was simpHfied, brought 
under a positive control and made entirely adequate and com- 
fortable. The air was forced through pipes in the pioneer tunnel 
and thence through the forward cross-cut to the main heading 
and back to the portal through the main heading. Stops across 
intermediate cross-cuts prevented short circuits. The venti- 
lation was so good that the heading blasting did not foul the 
workings where men were enlarging the heading. 

2. Work could be resumed immediately after blasting the 
enlargement holes. 

3. It permitted the drilHng of the center heading for subse- 
quent enlargement far ahead of and without interference from 
or with other blasting. 

4. The main heading muck could be removed through the 
nearest cross-cut and thence out through the pioneer tunnel, 
thus avoiding interference with the men and equipment engaged 
in enlarging the tunnel at other points. 

5. It served to conduct air, water and ventilation pipes to 
the heading without their being disturbed by the enlargement 
operations. 

6. Finally, it provided free access for men and materials to 
all points of the heading or enlargement workings at all times. 

The pioneer tunnel gave the further advantage of disclosing 
in advance the nature of the ground. Another point that 
developed was that the east and west portals of the main heading, 
which had to be driven through 1200 feet and 400 feet, respect- 
ively, of soft ground, required 12 months and 8 months, respect- 
ively, to do this work. If the driving of the rock main headings 

* Cf. Trans. Am. Soc. C. E., Paper 1390, Vol. LXXXI. Construction 
methods, Rodgers Pass Tunnel, by A. C. Dennis, Engineering Ne^i's, Vol. 75, 
No. 8, Feb. 24, 1916, pp. 382, 383, by J. G. Sullivan. 



HARD ROCK TUNNELS 503 

had been contingent upon these soft ground lengths the work 
would have been very much delayed. As it happened, the rock 
of the main tunnel Hne was reached by the first cross-cuts from 
the pioneer headings at the east and west ends in 4 and 2 months 
respectively after starting driving the pioneer tunnels. By 
going 60 feet and 150 feet above the main tunnel grade at the 
east and west tunnel portals and driving the pioneer tunnels on 
an incline, the soft ground work for them was more than cut in 
half. After the first cross-cuts above mentioned, others were 
introduced at intervals of from 1500 to 2000 feet. It is to be 
noted that the pioneer tunnels did not extend the full length of 
the main tunnel. A stretch of a mile near the middle of the 
tunnel was omitted, and that portion of the main heading driven 
from the last cross-drifts. 

The pioneer tunnel was 7 feet high by 4 feet wide. It is 
of interest to note that air hammer drills mounted on horizontal 
bars and using hollow steel with water attachment were used; 
that three drills usually, and four in tough rock, were employed. 
The average number of holes per round was 21 to 28. The 
rounds were usually 6 feet. Three 8-hour shifts were employed. 

The first set up of the drill bar was about 18 inches from the 
top. There was rarely any muck to be handled before this set 
up could be made as the bottom holes were heavily loaded and 
shot last to throw the muck away from the face. After the 
mucking was done the bar was dropped to near the floor and the 
balance of the round drilled. Shooting was done with fuse. 
Forty per cent and 60 per cent, gelatine was used. An average 
of 15 pounds per cubic yard was used in the pioneer tunnel. 
The cost of the pioneer is stated to have been $28 per linear foot. 

In the west pioneer tunnel the American hard rock record of 
932 feet per month was made. In the east, the best month was 
776 feet. The daily averages were 24 feet and 20 feet respect- 
ively. The pioneer tunnels were mucked by hand. Steel 
sheets were used and muckers loaded wheeled cars and rested 
in turn. Half -yard cars, hauled by mules conveyed the spoil 
back as far as the nearest cross-drift beyond which the enlarge- 
ment had proceeded, at which point they were taken through 



I 



504 MODERN TUNNELING 

the cross-drift and dumped into standard gage 12 -yard cars 
hauled by compressed-air locomotives to the dump. The one- 
half yard cars were not switched when empty at the heading, but 
overturned and rerailed when needed. 

The center heading of the main tunnel was 11 feet wide and 
9 feet high and its bottom was 6 feet above the subgrade of the 
main tunnel, with their center lines coincident. (See Figure 100.) 
This position of the heading enabled it to be made smaller without 
militating against the drilling of the enlargement holes as other- 
wise would have been the case. On account of water being pres- 
ent, a pair of headings was not drilled from each cross-cut, but 
instead usually only one, that in a westward direction. The 
system of driving was similar to that in the pioneer tunnels. 
The rounds averaged 7 feet and 3 2 holes were drilled in the hard- 
est rock. The average daily progress was 16 feet and 20 feet 
for the east and west ends respectively, and the maximum cor- 
responding monthly progress 631 feet and 762 feet, respectively. 
It must be remembered that driving of the main heading was 
in progress from several faces simultaneously. The men 
employed in the driving were given a bonus for exceeding a pre- 
scribed progress and earned it. When it was further agreed 
that the bonus, however large, would not be reduced, they earned 
still more. 

The main heading enlargement is a good example of the 
benefit to be derived from the engineering supervision of drilling 
methods. The enlargement drilling was done from two vertical 
columns on either side of the center line, each of which drilled a 
series of radial holes, as shown in Figure 100. The noteworthy 
point is that the engineering force located exactly the position 
of the columns and calculated the position and direction of the 
holes so that when drilled to the prescribed depths they termi- 
nated at a uniform distance — about i foot — beyond the theo- 
retical excavation line. Errors in the ahnement of the heading 
were thus obviated. The holes were pointed by clinometers. 

The series of holes were drilled about 6 feet apart as a rule 
but it was found cheaper to make them 5 feet apart when explo- 
sives increased in price. One of the results which the manage- 



HARD ROCK TUNNELS 505 

ment sought was to provide large quantities of muck for the 
power shovel which loaded the enlargement mucking. Hence, 
from four to twenty rings (from 20 feet to 100 feet of tunnel) 
were blasted at a stretch. It is to be noted that this blasting 
was done by batteries. The shovel loaded the muck into large 
cars of the size previously described, which were hauled to the 
portal by compressed air and beyond to the dump, by steam 
locomotives. The best monthly run for the shovel was 947 feet 
of tunnel at the east and 1030 feet at the west end of the tunnel, 
respectively. 

Summarizing the advantages of this method of tunnelling it is 
claimed that: "It enabled the heading progress, enlargement 
drilling, enlargement blasting and mucking to go on continu- 
ously without any interference whatever with one another." 

OVERBREAKAGE AND PACKING 

In further reference to the backing of lining considered on 
pages 447 and 448; any tunnel blasted in solid or loose rock 
involves irregularities in cross-section from the neat line estab- 
lished by the plans for the exterior Hne of permanent lining con- 
struction, by an indeterminate and very variable amount known 
as underbreakage or overbreakage of the rock section. The 
contractor is usually made responsible under the construction 
specification for this contingency of his work, excepting that 
in some contracts the necessary condition is recognized, by 
providing for payment for excavation, to a line (6) six inches, 
more or less, outside the neat line of permanent Hning con- 
struction; which might represent a percentage of overbreakage 
of something Hke 5 per cent, to 7 J per cent, over the neat section, 
depending on the general dimensions of the tunnel. This allow- 
ance would usually not be adequate to represent the actual 
overbreakage; and it is not important to the competent con- 
tractor whether any allowance is made, or not, providing it is 
definitely specified, in what way measurements for payments 
will actually be made; as the contractor will judge of the prob- 
able extent of overbreakage and packing likely to be incurred, 
and will make the necessary allowances in estimating on unit 



506 MODERN TUNNELING 

bid prices for contract. At the same time it is a matter of great 
importance that the contractor in estimating should allow an 
adequate margin to cover his construction costs, as it is not 
humanly possible (except with a Rotary Cutter in extremely 
soft rock) to avoid this loss, to a greater or less extent. 

The aim of every competent tunnel superintendent is to 
reduce the overbreakage to a minimum, but at the same time 
it is most desirable to avoid taking out the section too small, 
necessitating trimming to permit of lining to the neat section. 
Trimming, particularly in hard rocks, is slow work and involves 
very large cost per cubic yard removed, excepting in the case 
of occasional projecting points. In order, however, to obtain 
the neat section, a considerable overbreakage is necessary. If 
the rock is igneous and very hard, requiring heavy blasting to 
part it, the result is usually to break out large masses, even 
when the drill holes have been extended only a few inches beyond 
the neat lines. In stratified rocks, the breakage may be reduced 
by careful experimentation, as to the placing of the exterior 
line of trimming holes and light blasting. In such rocks as the 
shales of the carboniferous series, it is not uncommon for break- 
age to extend in pot holes or cones 8 or lo feet above neat lines. 

Illustrations are stated, elsewhere, of overbreakage involving 
from lo per cent, to 25 per cent, over the neat section of the finished 
tunnel. The relation of length of perimeter of lining to cross- 
section has a considerable bearing on the percentage allowable, 
as in a double- track large tunnel an allowance of as low as 7.5 
per cent, might be adequate while for a single track tunnel the 
figure might commonly be set at 15 per cent. This element of 
overbreakage involves, not simply the additional cost of drilling, 
blasting and mucking the excess quantity of unremunerative 
excavation, but it involves, further, the necessity for segregating 
that quantity of suitable loose rock, handling, hoisting and hand 
placing back of the finished lining to fill the voids. The pre- 
war cost of this backfilling and packing might range from 75 
cents to $1.50 per cubic yard in place, all which costs must be 
absorbed by the contractor, from what otherwise would repre- 
sent profit. 



HARD ROCK TUNNELS 



507 




CQ 



'^j^'/^^'^wii^m-irnvxii^'^'-'i^m^^^^^^^ 



508 MODERN TUNNELING 

The engineer should never overlook or neglect the absolute 
requirement that all voids should be tightly packed. If lining 
is required at all, it should not be subjected to the possibility 
of unsymmetrical earth pressures being imposed, by absence of 
packing, which may tend to destroy the arch. Where such 
earth pressures are great it is not uncommon to require that 
concrete lining be placed solid up to the actual surface of rock; 
in which case the overbreakage loss entails the further cost of 
concrete in place, instead of simply loose filling. 

"ROTARY CUTTERS" 

One other type of solid rock tunnel should be very briefly 
considered and that is the type represented by the proposed 
English Channel Tunnel of which short sections have many 
years ago been constructed. This is in chalk formation, a soHd 
rock able to support the pressures for a considerable period at 
any rate before Hning but which may be excavated without 
drilling or blasting. This has been done by excavating machines. * 
Two different types of machine were installed and used respect- 
ively on the French and English ends. These machines excavate 
by rotary action to a circular form for full cross-section. The 
J. D. B run ton machine, patented in 1866, installed and operated 
on the French end, utilized the principle of a revolving wheel 
pressed with great force against the face thereby spalling ofi 
slivers of rock which are delivered onto belt conveyor for de- 
posit into cars. An improved modern adaptation of the origi- 
nal Brunton tunneling machine has been recently brought out 
by Messrs. Brunton and Trier of Denver, Colo. (Figure 102.) 
The Beaumont-English machine, patented in 1875, operated as 
a rotary head cutting the face of rock. A number of new types 
of revolving machines have been patented and suggested for 
such a purpose, and certain types of the rotary cutter machines 
have been used with considerable success in small-sized tunnels 
in clay formations. Some of these consist of scoops revolving 
against the face and reproducing the action of a spade, feeding 

* Cf. The Engineer (London), Decern. 8, 1916, ff. 502-504. 



HARD ROCK TUNNELS 509 

the debris at the same time onto a conveyor belt. Very great 
speed of excavation is anticipated from such machines in the 
chalk. 

ADVANCED TEST DRILLING 

In soHd or loose-rock tunnels where there are known to be 
faults, or contacts with varying rock strata are anticipated, it is 
usually the measure of prudence to maintain ahead of the ''V" 
cut of heading excavation, advanced drill holes to a penetration 
several feet beyond the cut so as to disclose any possible great 
volume of water or bad ground which by sudden blasting might 
cause serious trouble. 



CHAPTER XXI 

LOOSE ROCK AND SOFT GROUND 
TUNNELS 

EXCAVATION METHODS 

A TUNNEL built through loose rock or soft ground needs 
temporary support to prevent caving in, before the permanent 
lining is placed. As has been previously mentioned only the 
American system of timbering will be considered in detail. It 
therefore becomes necessary at this point to describe what this 
system is. The essential feature of the American system is that 
the roof of the tunnel is supported by an arch formed of timber 
blocks or voussoirs. (Figure 103.) The spacing of these arches is 
governed by the need for support of the rock or soil. The 
foreign systems, on the other hand, have a general resemblance 
to one another in that the ground is supported primarily by 
longitudinal members or "bars," in turn supported by radiating 
props or vertical posts and with the back end of the bars some- 
times supported by the permanent lining. Figures 104 and 105. 
The American system is a development from the simple cap and 
legs of an ordinary small heading, developed to conform as closely 
as practicable to the shape of the roof of the tunnel. The early 
tunnels driven in this country, contemplated no other lining than 
the timber, and the general type shows a cap, two raking legs 
one on each side of the cap, and vertical posts supporting the 
rakers and in turn supported sometimes by a cross-sill extending 
across the whole width of the tunnel at subgrade. In certain 
cases a wall plate is interposed between the rakers and the verti- 
cal posts and in others the vertical posts are supported at their 
bottom ends by a separate wall plate or sill These designs, which 
date from the years 1820 to 1830, were almost invariably for 
single-track tunnels having a clear span never more than 19 feet 

510 



LOOSE ROCK AND SOFT GROUND TUNNELS 



511 



and usually of about 15 feet 6 inches. Although the three-piece 
system has been used for spans up to 26 feet, as in the Mus- 
conetcong Tunnel, Drinker says, that ''the variation from the 
three-piece form to multiple-block timber arching was first made 
by the late James Archbald, Chief Engineer of the Delaware, 
Lackawanna & Western R. R. in the construction of the Oxford 
or Van Nest Gap Tunnel in New Jersey in 1854; it proved most 
successful, and subsequently has been used in the construction 



e^fff^t^srt Hf^frt^ 



<*/-..'V.2J4 7 







--.-._• 



Fig. 103. American system of tunnel Fig. 104. General type of European 
timbering. system of timbering. 

of SO many tunnels, throughout all parts of the country, that it 
has become, in fact, the national system of tunnel timbering." 

It will be understood that longitudinal strength is given to 
the American system of timbering by stretchers or braces between 
the sets or bents of arch timbers. This is a most important 
point; without such strutting the American system would be 
most unstable. 

The system which has just been briefly summarized is capable 
of many modifications, and some of these will be described, start- 
ing with the simplest cases and working to the more difficult. 

The simplest instance is a rock tunnel normally self-sustain- 
ing but which requires some support for the roof to prevent 
occasional falls of rock from weathering, vibration, etc., as dis- 



512 MODERN TUNNELING 

tinguished from cases requiring resistance to live rock pressures. 
The heading for such a tunnel would probably be taken out to 
its full cross-section at one operation. The timbering will con- 
sist of segmental arches, usually of sawed timber spaced two, 
three, four or more feet apart. The only lagging which will be 
used outside the sets of timber will be here and there where the 
rock may be particularly loose. Packing and wedging will in 




Fig. 105. Typical sequence of operations in tunnel construction under 
English method 

most places be needed to give a bearing between the rock and 
the timber bents. The lower end of the bottom segments or 
blocks will rest on a hitch cut in the rock. Such a method of 
supporting the timbering can only be considered as temporary 
in character, as the weathering of the rock will inevitably destroy 
the support. Hence it will be usually economical, in the first 
instance, to have the lower ends of the bottom segments rest on 
a continuous longitudinal wall plate, which will be under-pinned 
by vertical posts in the same plane as the arch sets, after the 



LOOSE ROCK AND SOFT GROUND TUNNELS 



513 



bench has been taken out. The posts themselves will be sup- 
ported on foot blocks, transverse or longitudinal sills. Figure 
io6. 

The next case in order of difficulty is that of driving through 
rock which is not self-supporting, even during the short interval 
which might elapse between the time of excavating and placing 
the permanent lining. The general method of attacking such 




Fig, io6. American system of timbering Astoria gas tunnel, New York. 



work is first to drive a pair of small headings in which to place the 
two wall plates for the support of the full arch timbering. 
(Figure 103.) These headings themselves are usually timbered 
by simple square sets without lagging. After a length of wall 
plate has been set and the lowest leg of the full set placed, the 
next step is generally to drive a center top heading to enable 
the central member or members of the timbering to be set. 
These are supported temporarily by props to the floor of the 
top heading. Widening out from either side of the top heading, 
usually only to sufficient depth to enable the work to be carried 



514 MODERN TUNNELING 

out, will permit the balance of the main set to be placed. , The 
roof being now held, the remainder of the full heading can be 
done in safety. The next step for this kind of material will be 
to remove the bench and underpin the wall plate with posts. 

The next more difficult case is where the material penetrated 
is classed as soft ground, that is to say, ground which will run 
when opened up and in which therefore earth pressures are 
brought to bear against the timbers. The chief difference 
between this case and the last considered is that the completed 
timbering must be provided with lagging both at roof and sides. 
With the exception of boulders that may be encountered and 
which must be cautiously shot, no blasting will be necessary 
for the excavation of the material, which will be done by hand 
mining methods. 

As with the other cases considered, as far as American prac- 
tice is concerned, the location of the heading for soft ground 
may be either at the top or bottom. The latter has certain 
advantages where water has to be drained. It must be remem- 
bered that the chief aim of the American system is to build 
up the timbering system so far as possible by excavation 
around the periphery, so that the main portion of the exca- 
vation, or core, can be removed quickly and cheaply within 
the protection of the inserted timber. In soft ground such as is 
being considered, it is impossible to open large workings in any 
one operation without bringing the ground to a run, so that the 
entire excavation (excluding that of the core) is in the nature of 
closely poled or lagged timber heading work. See Figure 107. 

Whatever the location of the heading, it will be necessary, 
in the ordinary kinds of soft ground, to lag or pole the top and 
sides. In worse ground, the face also may have to be supported 
by close poling and in very wet or swelling ground the floor also 
may have to be timbered. Within the limits of a chapter it is 
quite impossible to give a detailed discourse on such a difficult 
and intricate art as that of heavy soft ground tunnel mining. 
Chapter XIV of this book touches on a few main principles 
apphcable to the ordinary cases and the bibhography at the end 
of this chapter gives a list of articles deahng with specific 



LOOSE ROCK AND SOFT GROUND TUNNELS 



515 



instances which should be studied by anyone with a problem of 
this nature in hand. In this type of work more than is custom- 
arily so in most engineering operations, the engineer will have 
to rely in a great measure upon obtaining the services of foremen 
and men skilled in this kind of work, as no amount of theoretical 
knowledge, unless aided by men skilled in these methods, will be 
sufficient to prevent disaster. 




Fig. 107, American system of excavating and timbering, 
hattan Railroad, Jersey City, N, J. 



Hudson & Man- 



If it is elected to do the work from the bottom, the usual 
course will be to drive the two advanced headings, one on the 
hne of each side wall footing, followed by a pair on the level of 
the wall plates. The dimensions of the headings will be selected 
with the idea in mind that when a pair on the same side have 
been excavated there will be sufficient room to put in the plumb 
posts, foot blocks and wall plates. Next there is the alternative 
of continuing to work upward, around the arch, putting in seg- 
mental timbers the while, or of beginning a central crown drift 
and widening down and out to meet the wall plates. 

It may be that it will be decided to start with a pair of wall 



516 



MODERN TUNNELING 



plate headings. Sub- 
sequently the sequence 
of excavation will be to 
complete the arch tim- 
bering, after which the 
underpinning of the wall 
plates can be done by 
one or more headings 
below them. Figure io8. 

Whatever system is 
used, the strictest care 
should be taken to min- 
imize the settlement. 

To the efficient exe- 
cution of any type or 
design of timbering for 
support of either rock or 
soft ground; the value 
of the timber Hning in 
fulfilling the intended 
function, is absolutely 
dependent on accurate 
fitting and solid block- 
ing and securing of every 
member. The accuracy 
of dimension and fit is 
necessary to produce a 
true structure to cor- 
respond with the design. 
The blocking and wedg- 
ing of every joint solidly 
to the exterior rock or 
soil is essential to main- 
tain the security and 
integrity of the complete 
set; otherwise there is 
a danger of kicking out 




LOOSE ROCK AND SOFT GROUND TUNNELS 517 

and collapse. Joints should be lapped with spiked plank to hold 
in position. Posts must always be thoroughly wedged to bear 
their full load and dapped into the wall plates or otherwise 
secured to maintain correct position. Head-sills must be scarfed 
and bolted to take longitudinal thrusts. In soft ground all poling 
boards must be slipped in back of posts and caps so as to obtain 
proper reaction and strapped to prevent kick out in case of under- 
mining. There is nothing in tunnel construction which so clearly 
indicates the efficiency of the miner as the regularity, uniformity 
and security of the timbering and nothing is so vital to the suc- 
cess of the work. 

For swelUng or running ground, which induces lateral pres- 
sures, the American system will have to be supplemented by 
the addition of transverse struts and bracing between the plumb 
posts. For aggravated instances of heavy pressure, running 
sand, swelling earth, etc., the tunnel shield may be the most 
economical as well as the most certain method of driving. This 
method is dealt with in the last section of this chapter. 

Needle Beams 
As an aid to construction of timbering in soft ground mining, 
the needle beam is invaluable. This consists of a stiff rigid 
beam held in stirrups attached to the crown timbers of the 
leading two or three completed timber sets and free to slide 
forward in the stirrups, having a length equal to about four 
frame spaces. This beam acts as a "cat head" or cantilever 
girder. When pushed forward a full frame space ahead of the 
leading set, it is wedged at the tail end against the cap timber 
and is then able to support, by blocking and wedging therefrom, 
the soil and timbers being set up for the next frame ahead or 
equally it can be used with blocks and falls or hoisting rig for 
hoisting timbers into place. The needle is commonly of timber, 
although if loads are heavy it is more usual and convenient to 
use a deep broad flanged I-beam from lo inches to i6 inches 
deep, according to the load to be carried. These needle beams 
can be used singly or in multiple, according to construction 
needs, the usual equipment being one in each heading, or in 



518 MODERN TUNNELING 

working out a full width heading for a Railroad Tunnel, com- 
monly two are used in pair. See Figure 109. 

Steel Sets 
It may be remarked that of late years it is becoming custom- 
ary to use steel I-beams instead of timbers for the sections of the 
arch timbering in bad ground. By its use several important 
advantages are gained. See Figure no. 

1. The outside flanges form a convenient support for the 
poling boards and a non-compressible support for such wedges 
as may be required. 

2. The inner flange serves as a shelf to support boards out- 
side of which concrete can be placed to fill the space out to the 
top lagging. This has the very important advantage of sealing 
off the ground from the action of the air, thus preventingjswelling 
or running. 

3. For equal strength the depth of member is less than that 
of wood, thus reducing the requisite amount of excavation. 

4. The quality of the steel is more uniform than that of wood 
and the members can be fabricated in a machine shop with a 
high degree of accuracy. 

5. The segments are united to one another by splice plates 
on either side of the webs of the segments and bolted through 
them through accurately drilled bolt holes. 

6. The abutting ends of the section are machined to give 
bearing value. 

7. The steel is more permanent than timber and not subject 
to rot or fire; this may be important if for any reason the work 
has to be shut down. It should not be assumed off hand that 
the first cost of steel sets is greater than that of timber, and the 
increasing use of steel and scarcity of timber tends to eliminate 
any difference against steel that there may be at present. 

The essence of soft-ground excavation and timbering is to 
prevent the movement of the ground or to reduce it to harmless 
proportions. Once ground starts to cave, the force it exerts is 
almost irresistible. Experience has shown that a useful means 
of preventing movement starting, is to open up and attack the 



LOOSE ROCK AND SOFT GROUND TUNNELS 



519 




Fig. 109. Use of needle beam in heading. 




Fig. 1 10. Steel I-beam sets for roof timbering. American system. Hudson 
& Manhattan Railroad, Jersey City, N. J. 

(The piles projecting through the roof were afterwards sawn off and the 
butts embedded in concrete lining.) 



520 MODERN TUNNELING 

ground by removing the lagging board by board, packing the 
lagging with hay, straw, manure, etc., grouting the ground i 
behind the lagging with cement, reducing effects of water pres- 
sure by draining, and in general to conduct every operation with 
extreme circumspection and skill. 

The extent and character of'timbering used may be greatly ' 
modified by outside conditions, as, for example, if such tunnel is 
being built in open country where external surface settlenaent is 
unimportant and no abutting property damage is incurred, 
there may be considerable economy effected in the timbering 
which would not be warranted when such work was being exe- 
cuted under the streets of a densely built-up city. 

Pilot Tube Method 
In soft-ground mining, considerable success has been attained 
in treacherous soil by the method developed by Anderson, in the, ■ 
first Hudson Tunnel in 1881* and later in the 16-foot diameter, 
main-relief sewer in Greene Avenue, Brooklyn, using a steel 
pilot tube instead of the usual heading and thereafter propping 
radially from the pilot tube as enlargement is carried forward. 
The "pilot" consists of a large steel tube about 6 feet diameter, 
aggregating about 40 feet long, consisting of smalk steel sheets ' 
connected internally by sraall angle irons bolted 'together. These 
sheets are taken down in the rear as they are put in place at 
the face to form the heading which thereby is continually 
advanced, the enlargement and permanent lining proceeding 
simultaneously. The pilot is driven as nearly as possible on^the 
central axis of the tunnel. 

Lining Methods for Rock and Soft-ground , Tunnels 

The type of lining to be used in any specific case, in accord- 
ance with the principles enunciated in Chapter XVII, necessi- 
tates the consideration in some detail of the actual work of 
placing the lining. In this connection the term lining is used 

* "Tunneling under the Hudson River," S. D. V. Burr. John Wiley & 
Sons. 1885. 



LOOSE ROCK AND SOFT GROUND TUNNELS 521 

to designate some type of permanent lining as distinguished 
from one of timber. 

In a tunnel of the cross-section of a railway or highway 
tunnel, it is usually inconvenient to build the entire perimeter 
of the lining at one operation, so that as a matter uf practical 
policy the placing of the lining will be divided into that of doing 

(a) The sidewalls with skewbacks to take the thrust of invert 

later constructed; 

(b) The arch; 

(c) The invert. 

It may be said that wherever possible the Hning should be 
built in the order stated, as by following this sequence, under- 
pinning, with the consequent tendency to subsidence, is avoided. 
Moreover, a better joint between an arch and sidewall and 
between a sidewall and an invert is obtained if the higher of the 
respective sections is placed after the lower. This question of 
good joint between the stages may be of great importance where 
there is water present in the ground and where a dry tunnel is 
desired. Where such water is under pressure and possibly adds 
to the earth pressure it is essential to approximate as closely as 
possible the design that has been prepared to meet such pres- 
sures. Where an arch is placed first and underpinned, with the 
sidewalls following, it becomes almost impossible to get even a 
fair approximation to the designer's ideal condition. Circum- 
stances may be seen to impose the necessity for constructing the 
arch first, but this should not be done until the point is made 
absolutely certain. 

In rock tunnels which are self-sustaining it may be possible 
to concrete the full section in one operation, although it is not 
often feasible. In short tunnels it may be advisable to post- 
pone lining until the excavation has been finished. 

As regards the use of forms for placing Hning, attention will 
first be given to those for concrete, either plain or reinforced, as 
this will be found to be by far the most common type of Hning 
to be used. For such a Hning in a tunnel, forms will be required 
for invert, sidewalls and arch, although if the invert is flat, forms 



522 MODERN TUNNELING 

will not be necessary. On the other hand no attempt should be 
made to build an invert with any appreciable curvature with- 
out a form. Due to the plastic nature of the material the 
result is generally unsatisfactory. 

Invert forms are designed to permit the concrete being 
poured from the sides and worked by spading and tamping to the 
center. This point must be borne in mind when suspending the 
forms, as also must the tendency of the plastic concrete to raise 
the form. It must not be forgotten that the invert form should 
make provision for whatever drains are embodied in the design 
and adequate V-shaped key-ways or dowels provided to ensure 
a bond with the sidewalk The length that may be attempted to 
be concreted in one time may vary within wide limits. As a sug- 
gestion, where possible it is desirable to make the length such 
that one shift of men can complete it. 

Sidewall and arch forms may be of wood or steel. If of the 
former the sidewall forms almost certainly will be set separately 
from the arch forms. The sidewall forms are filled by pouring the 
concrete from the top, the men standing on a temporary platform, 
the floor of which is approximately level with the top of the 
form. Wherever possible one or two men should be put in the 
form to work the concrete as it is deposited in order to keep the 
layers level, to produce as dense a product as possible and, by 
spading the plastic concrete back from the face of the forms, to 
give a smooth finished surface to the concrete. The way the 
concrete is brought to the working platform varies in different 
cases. In small work the concrete ingredients may be brought 
into the tunnel and mixed by hand or machine on the platform. 
Usually, however, this will interfere with the continuity of pour- 
ing, and it is preferable to bring the ready mixed concrete to the 
concrete gang, so that the latter only has to place the material. 
In such cases the mixed concrete is placed in watertight cars 
which are brought to the working platform, either being hauled 
up an incline or raised by a small elevator. Once the car is 
on the level of the patform it is dumped either onto the plat- 
form, whence it is shoveled by hand behind the forms, or, 
when the thickness of the side walls is sufficient, the contents 



LOOSE ROCK AND SOFT GROUND TUNNELS 



523 



of the car may be dumped bodily behind the forms. In order 
to get best results, it is important to build up the concrete in 
horizontal layers of not more than a foot or so at a time and 
to build the concrete up on each side at the same rate. Work 
should not be stopped until the form is completely ill led. 

Figure iii shows a t>T)ical set of such wooden forms. As in 
the case of the invert, key- ways, plum-stones or dowels should 




Fig, III. Wooden forms for invert and sidewalls, Astoria gas tunnel, 

New York. 



be inserted at the top of the sidewall to make a good bond with 
the arch. 

The arch forms are usually supported on cross-timbers set 
across the turmel between the sidewalls, to which they are tightly 
wedged or otherwise supported, further support being afforded 
by posts to the invert. The arch form is of the usual construc- 
tion namely, of ribs formed of segments of planking, spiked 
together and sawn to the required radius. These ribs support 
"lagging" w^hich are strips of planking laid horizontally over 
the ribs and built up from the bottom towards the top as the 
concrete is poured. Owing to the curvature of the arch, the 



524 MODERN TUNNELING 

width of the lagging should not be more than 4 inches, otherwise 
the finished surface of the arch will be irregular and probably 
not retain the cement when poured. There will be no necessity 
for beveling the sides of lagging of such width. It is not neces- 
sary to tongue and groove the edges of lagging, in fact it is pref- 
erable not to do so. The pressures induced by wet concrete 
are so great that the arch form, in general, will have the shape 
of a truss, with a horizontal lower chord and such intermediate 
members as may be necessary for the span and the thickness of, 
concrete being deposited. t 

In this connection the engineer is warned, to design the c^n^. 
ters for his work himself and not to allow the foreman carpenter; 
to evolve his own design. It must be remembered that the men- 
who are pouring the arch concrete have to stand .and , do their 
work between the ribs, so that the working space should ;be as 
free and unhampered as possible. This calls for rational design 
and for the ribs to be made as self-supporting as possible. Use- 
ful economy of space has been achieved by the .use of steel for; 
the ribs, particularly by the use of old rails bent to the neces- 
sary curvature. It is surprising what a difference a few insig- 
nificant inches of headroom may make in the possible speed .of the 
work. The concrete is brought to the pouring gang on the plat- 
form, which will be about the level of the spring line, in cars 
which are either hauled up an incline or raised by a small ele- 
vator, and shoveled from the platform into the space behind 
the ribs. The concrete should be brought up on both sides of 
the arch simultaneously, so as to avoid unsymmetrical pressures 
on the ribs and the surface of the concrete should be kept radial 
to the arch. After the concrete has been brought up on each 
side to within 18 inches or 2 feet of the center line on either side, 
this method of pouring the arch is discontinued and a special 
lagging rabbeted in order to support the key- or cross-laggings, 
(which are set transversely to the longitudinal axis of the tunnel), 
is set on either side of the center line. The arch is then keyed 
in, working from the back end of the length toward the leading 
end, filling the space between the already poured concrete on 
either side. It is usually necessary to mix the concrete for the 



LOOSE ROCK AND SOFT GROUND TUNNELS 525 

upper part of the arch and for the key somewhat stifTer and 
somewhat richer in cement than in the rest of the work, so that 
the fresh concrete may stand at a steeper slope and not flow out 
of the form. Owing to the inevitable shrinkage and settlement 
of the concrete it is inherently impossible to fill every void above 
the key and crown, and where such voids cannot be permitted, 
it is now usual to build in pipes leading to the outside of the 
concrete. Through these pipes cement grout is subsequently 
forced under air pressure, so that such voids may be completely 
filled after the concrete has thoroughly set. In placing grout 
pipes, it must not be forgotten that vent pipes for the escape 
of air are essential, otherwise the voids cannot be filled. In 
some cases it is not desired to build the concrete out to contact 
with the rock, but to fill the space beyond the specified thick- 
ness of the concrete arch, with some form of packing, usually 
of rock broken to a ''one-man" size. In such cases the rock 
packing is placed simultaneously with the concrete and the con- 
crete mixed stiffly enough not to incorporate any more than pos- 
sible with the rock which adjoins it. 

There are certain details of placing the concrete; the making 
of forms, etc., peculiar to concrete arches which are to be water- 
proofed on their exterior surface. These will be readily under- 
stood from what is said in the section on waterproofing in con- 
nection with what has been said just above. 

The arch forms should be rigid enough to prevent any 
appreciable settlement after the concrete has taken its initial 
set. They should also be designed so as to be easily dismantled, 
salvaged and re-erected. 

Collapsible Forms 
Tunnel work offers a good field for the use of the modern 
collapsible steel form, as the work is a continual repetition of 
the same cross-section, where this type of form shines to special 
advantage. (Figure 112.) The economy is gained by the saving 
of carpenters' time in erecting and moving the forms and in the 
saving of the large amount of lumber which is consumed for the 
forms in a tunnel of any length. The steel form is virtually 



526 



MODERN TUNNELING 



indestructible and as the surface, against which the concrete is 
deposited, is non-porous, the surface of the concrete is usually 
much smoother and denser than when wooden lagging is used. 
These forms are usually made in lengths of 30 to 50 feet, the 
length being governed by local conditions, and the sidewalls 




Fig. 112. Collapsible steel forms for tunnel arch lining. 

and arch are usually combined in one structure. The whole 
apparatus travels on a wide-gage track set on the tunnel invert, 
and the form is made collapsible so that it may be withdrawn 
from the surface of the concrete and moved forward through the 
already completed lining till it reaches the place where it is to 
be used again, at which point it is expanded once more to normal 
section, brought to line and grade and is once more ready for 
use. These forms are built by firms who make a specialty of 



LOOSE ROCK AND SOFT GROUND TUNNELS 527 

this apparatus and the engineer will do well to place the detail 
design for these forms in their hands, since their experience in 
this Une must be vastly wider than that of any individual. 
Quite marked economy and improved quality of work result from 
the use of these forms when the extent of the work for which 
they are to be used is considerable and involves a material 
number of repeats, and the possibihty of their adoption should 
be carefully considered in each case. In modern work of any 
magnitude, such forms are used almost as a matter of course. 

In these combined arch and sidewall steel forms, the side 
wall concrete will be poured first, from a level just above the 
spring Hne, the panels of steel plate, which take the place of 
wood lagging in such forms, being left out until the sidewall 
concrete is to grade, after which the panels are added as needed 
to retain the advancing concrete of the arch. These forms are 
equipped with mechanical hoists for raising the concrete to the 
upper platform ; in fact it may be said that these forms are self- 
contained units. 



PNEUMATIC PLACEMENT OF CONCRETE 

Of late years use has been made of compressed air to deposit 
concrete behind forms. This process is adapted to heavy work 
with aggregate measuring up to 4 inches or 4! inches diameter, 
if necessary. 

The plant required consists of a mixer, a pipe conveying 
system and a compressed air plant. 

The mixer consists of a steel shell, having a vertical cylindri- 
cal body and terminating at the bottom in an inverted cone. 
At the top is the door through which the materials are fed, 
unmixed, a batch at a time. The door is operated by a small 
air piston. It is opened by releasing the air in this cyHnder so 
that the door drops open by its own weight. At the bottom of 
the inverted cone chamber is a 90° elbow and this forms the 
connection to the discharge pipe. The door and the door piston 
are the only moving parts of the mixer and the inside is entirely 
smooth and free of obstruction. The main air jet is at the heel 



528 MODERN TUNNELING 

of the bottom elbow and this jet is the primary method by which 
the concrete is mixed and conveyed. 

The mixing and discharge are supplemented, however, by 
air jets which enter the mixer at the top. 

The conveying pipe consists of any standard smooth steel 
pipe with bolted flanges or any other convenient type of joint. 
An example of a conveying pipe is shown in Figure 8i, in the 
roof of the tunnel. The most rapid wear occurs at the small 
irregularities at the joints. 

For making deflections or turns cast elbows are used. Cast 
iron will usually last less than a day. Manganese steel is the 
most durable. 

A radius of 3 feet is the least that can be used for bends as a 
smaller radius will cause plugs in the Hne. 

To deflect or guide the discharge of concrete into the forms a 
series of sHghtly tapered pipes, fitting together like stove pipe, 
is used. Two or three of these sections, each about 3 or 4 feet 
long is all that is needed in a tunnel form for diverting the dis- 
charge from one side to the other. 

The compressor should compress to at least Sopounds per square 
inch; from this to 125 pounds per square inch is a suitable range. 

An air receiver must be provided to store at least 100 cubic 
feet with an additional capacity of 30 cubic feet for each 100 foot 
of pipe Kne and a greater capacity still if the mixer is more than 
300 feet from the compressor. 

The amount of air required varies with the specific gravity 
of the materials, the smoothness of the pipe, the number of 
bends and their radius, the distance conveyed (both horizontal 
and vertical) and the pressure and velocity of the air. For the 
usual size of mixer the amount of air required has been found to 
be 2 cubic feet of actual free air at 100 pounds per square inch 
for each linear foot of pipe per batch, e.g., to convey one batch 
500 feet it will require 1000 cubic feet of actual free air at 100 
pounds per square inch. 

Concrete has been conveyed up to 4900 feet in an 8-inch 
pipe with a 16 cubic foot mixer. This was at the Twin Peaks 
Tunnel at San Francisco. 



LOOSE ROCK AND SOFT GROUND TUNNELS 529 

The plants may be stationary or portable. 

Tests show that concrete deposited by this method will 
develop a crushing strength up to 3000 pounds per square inch 
with two parts of stone to one part of Portland cement. 

With eight parts to one, a crushing strength of 1400 pounds 
per square inch was developed. These tests were on 12 -inch 
cubes, tested at 30 days. 

Blocks of a tunnel Hning were cut out. These blocks were 
from 9 inches to 1 2 inches square and from 1 2 inches to 20 inches 
high. The crushing strength ran between 1200 pounds to 3000 
pounds per square inch and the average was 2000 pounds. 

Incidentally, it has been found that these mixers will effect- 
ively place dry rock packing in the form of broken stone 
crushed to sizes of dry concrete aggregate and in places where 
it would be difficult or impossible for men to work. 

The same advantage holds good for placing concrete and the 
system seems to have special application for such cases as the 
relining of tunnels under traffic, where the question of allowing 
clearance for the trains through the concreting operations is a 
controlling factor. 

The work is one of those special varieties where the engineer 
should call in the expert and thus gain the advantage of the 
specialist's wide knowledge of the possibilities of the method, 
rather than to waste time and money on experiments which 
might be avoided. 

The information given here has been taken from a paper by 
H. B. Kirkland, printed in the ''Journal of the Western Society 
of Civil Engineers," May 13, 1918. 

Supplementing the foregoing information and, as the result 
of further experience, the following points may be added. 

Concrete may be pre-mixed before blowing, using an ordi- 
nary rotary mixing machine for preparing the batch, or may con- 
sist of unmixed materials which are satisfactorily mixed in transit 
through the blower and pipe system by adjustment of the air 
jets in the blower. 

Better success is commonly obtained by keeping the convey- 
ing pipe line in an upwardly inclined position. There is a tend- 



530 MODERN TUNNELING 

ency for the air, if not applied correctly, to travel through the 
thinner material, or over the top of the mix, leaving the stone 
to drag along in the bottom of the pipe. This tendency is 
reduced by creating a resistance to the air by inclining the line 
upwards, so that there may be a head to work against. In 
blowing concrete, it is vitally necessary to prevent plugging 
in either the blower or pipe line. The assumption that the 
batch should be premixed very wet is erroneous as it is usually 
easier to maintain perfect discharge and prevent plugging when 
blowing ''jelly" concrete instead of ''soupy" concrete; as in 
the latter case, the water segregates from the solid matter. 

In freeing the line or blower from plugs, by hammering or 
pounding it should be seen that air pressure is shut off at the 
same time, as tending to tighten up the plug instead of freeing it. 

Nozzles of rubber or of hard steel may be used. The wear is 
very rapid and the latter are usually more economical and give 
better results. 

The blower operates best when controlled by one man, the 
air valves being so arranged as to permit one-man operation. 
The bottom air is the primary force and is always applied first, 
about 5 to lo seconds before the top air is applied. This bottom 
air starts the materials travelling through the pipe from the 
blower while the top air, or secondary force, feeds the mix to 
the bottom air. The top air should never be applied first as 
this plugs the mix in the bottom of the blower. 

The door should be kept free and clean of the mix. When 
blowing unmixed materials, this is -no trouble as the materials 
are dumped into the blower dry, while the water enters the blower 
through a separate pipe. When blowing premixed concrete, the 
mix is dumped generally over the door sill, though chutes are 
sometimes used. The mix should be cleaned from the door and 
frame, otherwise the door will leak air, resulting sometimes in 
a plug and in tearing the rubber gasket. 

When properly blown the mix should leave the nozzle in a 
steady flow, like meat from a sausage machine; not in spurts 
of water, and concrete, at intervals. 

The prevention and immediate removal of plugs, and the 



LOOSE ROCK AND SOFT GROUND TUNNELS 531 

cleaning out of the blower and conveying line at the end of the 
shift, are important. The materials should be watched to pre- 
vent large pieces entering the blower. The cleaning should be 
done by blowing one or more batches of water after the work 
is finished and it is well to also blow a batch or two of dry stone 
or gravel through, as this scours the pipe. 

A system of operating signals, from the form to the blower, 
is also essential. 

Steel forms should, if possible, be used with blower concrete. 
If wood is used they must be sheathed, where nozzle discharges, 
with sheet iron for protection. Blower concrete is used more 
satisfactorily where reinforcement is npt used, as the velocity 
of discharge is very Hable to displace the reinforcement. The 
discharge nozzle should be moved frequently to prevent seg- 
regation of aggregate and the concrete deposited must be well 
spaded and the unfilled skin of the form kept clean of splash. 

Precast Block Lining 
As pointed out previously, another form in which concrete 
can be used is that of pre-cast blocks. By this use of concrete 
the necessity for forms for the invert and sidewalls is avoided, 
all that is needed being mould boards to guide the masons. In 
the arch, centers will be required to support the blocks until 
they are keyed up, but close lagging will not be necessary. 
While this use of concrete may be better adapted for tunnels in 
more or less self-sustaining ground, it has considerable possi- 
bilities for other kinds of ground, as the operations in the tunnel, 
where labor is more expensive, are reduced. It has one other 
advantage in that the extrados of the arch formed of such blocks, 
affords a smooth surface on which waterproofing may be laid. 
The concrete having reached its final set before being placed in 
the tunnel, the flow of water cannot harm it. In general, the 
use of blocks eliminates a good deal of skilled labor. 

Brick Lining 
As has been previously mentioned the use of brick for tunnel 
lining is on the decline and the tunnel brick-layer is virtually 



532 MODERN TUNNELING 

extinct. In essence the work resembles that of the concrete 
block, with very much smaller units and consequently much 
more labor in laying. It is particularly important that no settle- 
ment occur in the arch forms. The brick should have a uni- 
formly high crushing strength, and be laid in Portland cement 
mortar. Care should be taken to see that there are ample 
headers and that the joints are properly broken. The bricks 
should be soaked in water before being laid, in order not to absorb 
the moisture from the mortar. A wire-cut brick is usually better 
than a pressed brick as its rougher surface gives it a better 
adhesion to the mortar. For first class work, it is used to specify 
the thickness of the mortar bed, which should be kept as low as 
possible, say from one-quarter to three-eighths of an inch. After 
a length of arch has been keyed up, it is proper to slack down the 
centers a httle, so that the mortar may attain its set under the 
pressure of the brick work. 

Cement Gun 
Another method of placing a lining which is thin or of repair- 
ing an existing lining is by the use of the cement gun. This 
machine blows, under air pressure, a mortar of sand, cement and 
water against any surface it is desired to cover. It is necessary 
to place the gunite, as it is called, on a metal lath v/hich may be 
triangular or square wire mesh, or even, in light cases, of ordi- 
nary chicken netting. The gunite is built up in thin layers on 
and around this lath and forms a very dense a.nd strong mass of 
reinforced mortar. Usually the thickness of such a structure 
will not be more than 3 or 4 inches and the process has great 
advantages in cases of repair to existing concrete structures, the 
covering of exposed steel work and as a means of covering a sur- 
face of rock which is self-sustaining but which is Hable to spall 
under weathering. The great density and strength of gunite 
lies in the fact that the impact of the mixture as it rushes from 
the nozzle against the surface to which it is being appHed, 
causes a rebound of the inert portions of the cement, together 
with some of the sand, thus eliminating useless constituents. 
In using a cement gun it must be absolutely certain that the sand 



LOOSE ROCK AND SOFT GROUND TUNNELS 533 

and cement are dry passing through the machine until hydrated 
by the water supply at the nozzle as otherwise the hose will 
become clogged and inoperative. 

Liberty Tunnels 

As a recent illustration of loose rock tunnels, now in process 
of construction, the following information obtained through the 
courtesy of A. D. Neeld, Engineer in Charge for the County of 
Allegheny, Pa., and J. C. Scott, Resident Engineer; is given as 
elucidating the subject under consideration. The twin Liberty 
Tunnels are to pass through Mt. Washington on south side of 
Monongahela River at Pittsburg, Pa., to serve for Highway pur- 
poses. The contractors are Booth & Flinn, Ltd. 

The design provides two tunnels, 59 feet apart between 
centers, and extending from the south side of Mt. Washington 
at Warrington and West Liberty Avenues, to the north side at 
Carson Street, at about 1000 feet east of the existing Mt. Wash- 
ington tunnel. The tunnels, with approaches, are each 6280 
feet long, and the tunnels proper, from portal to portal, are each 
5690 feet long. Both tunnels are carried at the same elevations 
and the gradient is ^ per cent downward from the south portal 
to the north. 

Trafific is to be operated in one direction only, in each tunnel, 
south to the city in the East Tunnel and north from the city in 
the West Tunnel. 

Both tunnels are identical in cross-sectional design, except- 
ing that the positions of the sidewalk, sewer, roadway, and rail- 
way tracks, are reversed in each. 

The tunnels are concrete lined and have a maximum finished 
height of 20 feet 7 J inches above the roadway, and a maximum 
finished width of 26 feet 6 J inches. The finished tunnel provides 
one street railway track, a vehicular roadway for one line of 
traffic, and a footwalk. 

The railway track is on the opposite side of the tunnel from 
the footwalk and is constructed of 4|-inch by 84-inch steel ties 
laid on a 6-inch stone ballast roadbed and concreted in. Power 
will be supplied the electric cars from an overhead trolley. 



534 MODERN TUNNELING 

The roadway is 13 feet 3! inches wide from the track rail to 
the opposite curb. It is constructed of 4-inch vitrified brick 
paving laid on a J-inch sand-cement cushion overlying a 6-inch 
concrete base. The brick paving extends between the track 
rails and to the opposite curb so that the roadway, for emergency 
use over the tracks, is 21 feet wide. 

The footwalk is 4 feet wide and 10 inches above the roadway 
and is on the opposite side of the tunnel from the tracks. Pro- 
tection is afforded the pedestrians by a pipe railing 42 inches 
high. A 14-inch by 30-inch space is provided under the footwalk 
for telephone ducts. 

A 1 5-inch diameter terra cotta sewer, with concrete manholes 
500 feet apart, extends through the tunnels on the sidewalk side, 
as well as a 6-inch water main. 

The plan provides a 24-inch concrete arch to a radius of 13 
feet 3 J inches, reinforced with i-inch twisted steel rods on 
18 inches centers. A 3 -inch enameled wrought-iron electric 
light conduit is carried along the centerline in the crown of 
the arch, with junction boxes for 100 Watt lamps every 50 feet. 
The trolley feeder line is supported by two f-inch by 18-inch 
expansion eye bolts set in opposite sides of the arch, every 
50 feet. 

The arch is supported on concrete sidewalks, 24 inches thick 
at the spring line, and battered down to 27! inches thick at the 
curb line (78 inches below spring line). 

The side walls are supported on concrete footings, differing 
in dimensions. On the sidewalk side the footing is 36! inches 
wide and extends to the bottom of the sewer trench, 68 inches 
below curb line. On the opposite side the footing is 39! inches 
wide and extends 54 inches below curb line. 

The tunnels are being driven through soft laminated rock, 
consisting of shales and fireclays, with some harder sandstones. 
The rock is not self-supporting and as a tunneling material is 
undesirable, as it requires continuous timbering and cannot be 
opened up for any length of time without strong and sound 
timbering being immediately placed. An 8-foot heading advance 
requires timbering before the expiration of 24 hours, and this 



LOOSE ROCK AND SOFT GROUND TUNNELS 535 

advance has been found to be the maximum that may safely 
be opened at a time. 

The sandstone is a grayish blue, generally stratified, and 
easily worked when not folded with the softer shales and fire- 
clays. It does not weather upon exposure and does not usually 
develop water. It offers a firm footing for the heading timber- 
ing and is more easily drilled than the softer rocks, especially 
the clays and decomposed shales, which plug up the air exhaust 
holes in the drill steels. It is the common building stone for 
cellar foundations in this section. 

The shales are extensively laminated, soft, and difficult to 
blast without shattering, but not as much so as some of the 
fireclays. These shales run in thin layers, often with the cleavage 
planes of a greasy soaphke film, that results in sHdes if not 
immediately timbered, and is especially treacherous if water 
develops, as this soapy film deteriorates rapidly when wet. 
The shale proper weathers quickly upon exposure to the air, 
and it has been found to lose any dependable strength after 
about three weeks' exposure. 

The fireclays are not hard, but may be distinguished as 
hard and soft. They are found in both stratified layers and 
unstratified masses. Usually the cleavage planes are of the 
greasy, soapy, film noted above. This film contains quite a 
little lime but the rock proper does not. The soapy film, when 
tested with hydrochloric acid, develops an agitated reaction, 
while the rock so tested shows no reaction at all. 

The softer of the fireclays is a reddish brown in color, and 
does not appear to be affected by exposure to the air, but if 
immersed in water, it flakes off immediately and in ten to fifteen 
minutes, it is reduced to a finely pulverized substance. Fortu- 
nately, no water has been encountered during the driving of the 
tunnels through the fireclays and, in fact, the rock has been 
absolutely dry excepting for the first two or three hundred feet 
in from the portals, where only a little water was met, not more 
than a trickle at any one place. 

The harder of the fireclays is green in color and Hke the 
brown, has the soapy cleavage planes. It is very brittle and 



536 MODERN TUNNELING 

shatters badly from the blasting, requiring immediate propping 
even during the erection of the heading timbering. It is not 
affected by water as is the brown, and while the rock proper 
does not appear to weather, it splits up along the soapy planes 
after exposure. The air appears to dry these soapy planes into 
a white limelike powder that allows the rock to split up. Intru- 
sions of iron pyrites have been found in this green fireclay. 

The contract price includes the completed construction of 
the tunnels from portal to portal, as shown on the contract 
plan, while the approach work is to be done by the tunnel con- 
tractors at various unit prices, in addition to the tunnels proper. 
The tunnels when completed will cost about $5,000,000, which 
represents approximately $400 per lineal foot. 

The tunnels are being driven from one end only, the south, 
mainly because of the fact that this end offered cheaper dis- 
posal of the spoil than did the other end. 

The foundations for the plant buildings were started about 
January ist, 1920, while the tunnels were not headed until 
May ist, 1920. To date the tunnels have been driven 750 and 
780 lineal feet each and work is now going on at the rate of an 
8-foot advance in each tunnel daily. 

These tunnels are unusually large, with a consequent large 
volume of rock, spoil and concrete, to be handled daily, so that 
one of the chief difficulties is the question of tunnel transporta- 
tion. A system has been developed that gives an admirable 
solution to this problem, and it appears to be the most economical 
that can be devised with the existing plant and local conditions. 
This system consists of the following daily routine : 

7 p. M. to II P. M. Drilling heading and jDcnch. 
Blasting heading and bench. 
Mucking out heading for timber wall plates. 
Concreting. 

Erecting and packing heading timbering. 
Disposal of muck from tunnel. 
Moving, setting and fitting up concrete forms. 

This arrangement permits of the use of the tracks at night for 
hauling the concrete and for the hauling of the spoil in the day- 
time. 



Night Shift 


II P. 


M. 


to 


I A. 


M. 




I A. 


M. 


to 


4A 


M 




7 P- 
7 A. 


M. 
M. 


to 
to 


7 A. 
2 P. 


M. 




M. 


Day Shift 


7 A. 
7 A. 


M. 
M. 


to 
to 


4 P. 

5 P. 


M. 
M. 



LOOSE ROCK AND SOFT GROUND TUNNELS 537 

The tunnels are being driven by the top heading and bench 
method, with the bench face kept within lo feet of the heading 
face. This has proved the best method in every respect, both 
from the point of speed and economy, as well as safety. With 
the bench face close to the heading face, the heading muck is 
thrown over the bench by the blasting, to the invert below, 
where it, together with the bench muck, is loaded into cars by 
a Marion shovel. This reduces the amount of hand mucking, 
and the consequent repeated handling of the muck, to a mini- 
mum, as very little time is required to clear the shift length of 
bench for wall plates. The use of a mucking machine, with a 
necessarily longer bench, would have required additional hand- 
ling and costs. 

The full width tunnel heading is carried, being about 15 feet 
high and 35 feet wide. As the rock is not self-supporting, the 
whole length of the headings has been timbered and it is believed 
that this will be necessary for the entire length of the tunnels. 

The heading timbering consists of 8-inch 32 J pound segmental 
steel H beams, covered with 3 -inch yellow pine lagging. Each 
set of steel segments, or ''ring," is made up of 7 segments bolted 
together in the tunnel as erected. The five upper segments 
are each 6 feet 4 inches long and cut with radial joints. The 
leg segments on each side are each 6 feet long, cut with a square 
joint, and have a 15-inch steel foot plate riveted on the base. 

The rings are erected on 1 2-inch by 1 2-inch yellow pine wall 
plates cut and set in 8-foot lengths, and recessed out to fit the 
footplates. 

The steel rings have been erected on 42, 48, 54 and 60-inch 
centers, depending on the progress attainable and the nature 
of the rock. In general, the 48-inch span is about the maximum 
safe limit. 

The positioning of the rings is made by two f-inch tie-rods 
and two 3-inch by 6-inch timber joggle blocks, to each segment, 
and the latter are wired to the tie-rods to prevent displacement 
by the blasting. 

The space between the lagging and the rock is dry packed 
with sound rock and, after the construction of the concrete 



538 MODERN TUNNELING 

lining, this packing will be grouted with a cement-sand mix of 
I to I. The space behind each joint is rigidly blocked to the 
rock with short 1 2-inch posts and the packing is well placed to 
protect this blocking from displacement by the blasting. 

Two-inch grout pipes are set in through the 3 -inch lagging 
as the heading is timbered, and carried back into the high, or 
wide, points in the packing. Three such pipes are set every 
25 feet, one in the crown segment and one in each haunch, and 
these pipes are extended through the arch form, before concrete 
is placed. Additional pipes are also set in the arch form, under 
the foot-plates and the grout will be injected through these 
additional pipes, using the haunch and crown pipes as tell-tales, 
or for injections if necessary. 

The bench is shot down to the bottom of the concrete side- 
wall footings, as it is believed to be more economical to remove 
this extra muck with the shovel than to later cut out trenches 
in the rock invert. Rock fill will be placed in the low invert to 
the bottom of the concrete roadway base. 

All drilling is performed with small one man dry machines, 
some Ingersoll-Rand Butterfly drills and some Denver Rock 
Drill "Nineties," with compressed air power. 

From 24 to 30 holes are drilled in the heading face, consist- 
ing of 2 rows of cut-holes of 4 holes each, and started about 4 
feet on each side of the center-line, while the balance of the 
holes are spread over the face on each side of the cuts, about 
4 feet apart. The cut-holes are 10 feet deep and give a pull of 
8 feet while the other holes are 9 feet deep. 

The bench is drilled with two rounds about 4 feet apart for 
an 8-foot advance. Generally, 16 holes are drilled, 6 in each 
round, vertical, and 4 lifters or toe-holes, the cuts 12 ft. deep 
and the lifters as necessary. 

The blasting is done with 40 per cent, dynamite, in i-inch sticks 
of 0.6 pound each. The heading holes are loaded with 4 or 5 
sticks each, or 2.4 to 3 pounds each. The bench holes are 
loaded with 10 sticks, or 6 pounds each. The blasting averages 
about I pound of dynamite to the cubic yard of rock. 

A Marion shovel of ij cubic yard capacity, is used in loading 



LOOSE ROCK AND SOFT GROUND TUNNELS 539 

the muck from the foot of the bench into 3-yard side dump 
cars. The shovels are operated with compressed air, and the 
air exhaust from the shovels is an aid in ventilating the head- 
ings. Two 30-inch gage tracks of 8o-pound rails are laid on 
the tunnel invert and the muck is hauled in 6-car trains. The 
haulage in the tunnels is made. with electric locomotives, while 
outside to the dump it is performed with steam locomotives. 

The dump is in a public park about J mile from the south 
portal and is reached up a 6 to 7 per cent grade. Two 6 car 
trains are operated back and forth to the dump, one pushed by 
a large Climax geared locomotive, and the other pushed by 3 
small dinkey locomotives. The round trip requires about 12 
minutes and from 65 to 75 cars of muck are taken out of each 
tunnel daily, depending on the nature of the rock as the softer 
rock breaks smaller and can be more solidly loaded. 

The heading and bench work is done by "piecework," the 
men being paid for 11 hours each shift and allowed to go off as 
as soon as the daily advance has been attained, as 7, 8, or 9 feet, 
depending on the ring span decided upon. 

The drilling, blasting, and mucking out for wallplates, which 
are all performed on the night shift, are generally finished by 
3 or 4 A. M., while on the day shift the timbering is usually com- 
pleted by I or 2 p. M., and the muck disposal by 3 or 4 p. m. 

Only two shifts, of 10 hours each, are worked daily, and on 
six days a week. 

The concrete lining is being placed at night and at present 
about 650 feet of each tunnel is lined complete, with the exception 
of the concreted roadway base, which is not considered as lining, 
and the final grouting of the concreted lining. This latter has 
not yet been started. 

Two Blaw Knox steel forms are used in each tunnel, one 
35-foot side- walls form, and one 25-foot arch form. Additional 
wooden forms, both sidewalls and arch, were used in emergency 
to expedite the concreting in order to cover some sections of 
sliding rock. 

The concreting plant is about 500 feet from the south portal 
and located on a spur of the Wabash Railroad and materials 



540 MODERN TUNNELING 

are delivered by freight. A trestle has been constructed on the 
side of a hill and 7 sand and gravel bins built underneath, each 
about 16 feet by 25 feet by 12 feet deep, and sand and gravel 
are delivered in hopper cars and dumped directly into the bins. 
These bins are piped and steam heated to prevent freezing of 
the materials during the winter. Two cement sheds are built 
on top of the trestle, one on each side of the track. The mixing 
plant is under the bins and the mixed concrete is hauled in side- 
dump " V " cars of 4 cars to a train. 

All concrete is of gravel aggregate of i : 2 : 4 mix, the materi- 
als being Alpha Portland cement and Allegheny sand and gravel. 
The cement is tested at the mills while every car of sand and 
gravel is tested at the tunnels for organic matter and percentage 
of loam. 

The concrete lining is poured in 3 different operations and 
sections as : sidewall footings, sidewalls, and arch. 

The footings are poured with wooden forms in about 50-foot 
sections the mix being dumped onto platforms on the tunnel 
invert and shoveled into place, 6-inch by 6-inch wooden key 
strips are laid into the top of the footings and sidewalls, for 
bonding the structures. 

The steel sidewall form has a plank decking across the top 
just above spring line and is attached to a travelling steel inclined 
track, about 80 feet long. The cars are pulled up this incline 
with a cable attached to an electric locomotive running on the 
tunnel invert tracks. The concrete is dumped onto the decking, 
and shovelled behind the form. The concrete is spaded in the 
forms, but is not tamped other than the tramping of the spaders. 
The concrete is mixed as dry as workable and requires consider- 
able spading for this reason. The spades are perforated with 
10 or 12, ^-inch dia. holes in order to secure a good finish. 

The arch concrete is blown into the form through a i-yard 
Caniff blower. This blower is secured under the steel sidewall 
form decking, and the cars are hauled up the incline and dumped 
into the blower dumping box. The concrete is blown with 
about 80 pounds air pressure, 100 to 200 feet through a 6-inch 
discharge line. A branch tee is used on the end of the discharge 



LOOSE ROCK AND SOFT GROUND TUNNELS 541 

line, distributing the mix to each side simultaneously. The 
wooden joggle-blocks are removed just before concreting a sec- 
tion while the tie-rods are left in place, and to these the steel 
arch reinforcement is securely wired. The grout pipes through 
the steel ring lagging are extended through the form section to 
the form skin, while additional grout pipes are placed, one 
between each steel ring, from under the lagging to the skin. 
These latter pipes are for flood grouting of the concrete arch, to 
fill any voids that may exist in the lining proper, up under the 
lagging. 

With these methods of concreting the chief item is the prep- 
aration of the forms, the actual placing proceeding faster than 
the forms can be moved, set, and fitted, as the forms are not 
stripped until i8 hours set. Placing sidewall concrete is of 
course the cheapest and quickest operation; but the blowing 
of the arches has been developed exceptionally well. When 
blowing the arch concrete, an average of 6 trains, or 24 cars 
totaling 16 cubic yards, is placed each hour, or 200 cubic yards 
for a 12-hour shift. In an emergency period over 1700 cubic 
yards of arch concrete were blown in a week, concreting 325 
lineal feet of arch. 

The footings have averaged i.i actual cubic yards of con- 
crete per lineal foot of tunnel, the sidewalls 1.5 cubic yards, and 
the arch 5.2 cubic yards, or a total of 7.8 actual cubic yards of 
concrete lining per lineal foot of tunnel. 

The rock packing averages about 1.75 cubic yards (of space) 
per foot of heading, or an overbreakage to the timbered design 
of about II per cent. The actual excavation exceeds that 
required by the Construction Plan about 30 per cent in the head- 
ing, 37 per cent in the bench, or a total of about ^1, per cent. 

Electric power for plant operation is purchased of the 
Duquesne Light Company. The principal plant equipment con- 
sists of 3 Ingersoll Rand 1200 cubic foot air compressors; two 
I J yard Marion shovels; one Ransome and one Foote, i- 
yard rotary concrete mixers ; 4 Canift' concrete blowers ; 2 Caniff 
grout machines; Butterfly Jack hammer and Denver Ninety 
rock drills; Lakewood steel V concrete cars; 3-yard side dump 



542 MODERN TUNNELING 

muck cars ; 4 Westinghouse mine locomotives (electric) , 3 dinkey 
steam locomotives; i Climax geared steam locomotive. 

The comparative labor costs of the heading and bench work 
are given below, on the basis of the daily 24-hour payroll taken 
as 100 per cent. These percentages only cover the direct labor 
at the point of work. The discrepancy between their totals 
and the igo per cent, basis, represents supervision, plant oper- 
ation and maintenance, and miscellaneous charges. This com- 
parison covers a period when no concreting is being performed, 
and therefore represents the labor costs per lineal foot of exca- 
vation. 

Daily 24-hour payroll 100 . 0% 

Heading: 

Drilling, blasting, and mucking for wallplates 12.2% 

Timbering 26.1 

Muck disposal 11. 9 

Heading Total 50.2 

Bench : 

Drilling and blasting 1 1 • 5% 

Muck disposal 11. o 

Bench Total 22.5 



As the disposal of the muck from the heading and the bench 
is a single operation, the above percentages for this item were 
distributed on a yardage basis. Below is given an itemized 
distribution of this disposal cost. 

Disposal of IVi'ick: 

Loading 9-2% 

Tunnel transportation 4.7 

Dump transportation 4.1 

Dumping 4.9 

Disposal Total 22.9% 

COST OF SOFT GROUND TUNNEL 

A good illustration of the uncertainty of results obtained in 
estimating the cost of soft ground tunnels is that of the Flat- 
bush Avenue double-track railroad for New York City rapid 
transit service alongside Prospect Park, Brooklyn. These tun- 
nels are throughout in soil consisting mostly of sands and gravels 



LOOSE ROCK AND SOFT GROUND TUNNELS 543 

of varying quality with earths and some small boulders, the 
general character of which was ideal, the roof being at an aver- 
age depth of approximately 55 feet below the surface. The 
contract involved simply three shafts for access and to allow 
of prosecution of the work, in addition, to the twin tunnels 
designed with a central concrete wall. The entire excavation 
was taken out by mining methods, timbering and concrete 
permanent Hning having semicircular arches and segmental 
arch inverts. Practically no water was encountered as the loca- 
tion was entirely above the level of ground water. The length 
of the structures from end to end was 4310 feet. Total exca- 
vation in tunnels 134,000 cubic yards. The contract bids were 
opened February, 1916, twelve bids being received from exper- 
ienced contractors and which ranged for the complete work, 
from $1,370,098 (low) to $2,610,892 (high), the average aggregate 
being $1,716,000. The two largest items of construction ranged, 
for excavation in tunnel including timbering, from $4.30 to 
$12 per cubic yard and for concrete in tunnel lining from $7.50 
to $15 per cubic yard. 



CHAPTER XXII 
SUBAQUEOUS TUNNELS 

The use of tunnels for the crossing of rivers or bodies of 
water for railways is one of the resources of the engineer that 
has developed within the last half century. Although Brunei's 
Thames tunnel was completed in 1843, ^-nd was constructed as 
a highway tunnel it was never used as such, but has been used 
for railway purposes since 1866. The use of subaqueous tun- 
nels as part of the city passenger transportation system of such 
cities as London, Paris, New York, Boston, Glasgow and Liver- 
pool, has become quite usual, but such tunnels have not been so 
generally used by trunk Hne railways. The following are the 
chief trunk line railway subaqueous tunnels: The Sarnia tunnel 
of the Grand Trunk Railway crossing the St. Clair River, the 
Detroit Tunnel of the Michigan Central Railway, the Pennsyl- 
vania Railroad tunnels under the Hudson River, and the Long 
Island Railroad tunnels under the East River, both to afford 
access to the Pennsylvania Terminal in New York City, the 
Severn tunnel of the Great Western Railway in Great Britain, 
and the Mersey River tunnel on the line of the Mersey Railway 
at Liverpool, England. 

In contradistinction to bridges, the cross-section of a tunnel 
is independent of the width of the span of the waterway to be 
traversed, hence there is no necessity to provide at any one 
place any more tracks than the traffic requires at that point. 

If the amount of trafhc justifies additional tracks crossing 
the stream they can generally be built at some other point con- 
venient to the traffic. 

Most subaqueous tunnels have been built in soft ground by 
means of a shield with the aid of compressed air, although they 
have also been built in rock without air pressure or a shield, the 

544 



SUBAQUEOUS TUNNELS 545 

Mersey tunnel, the Severn tunnel and the Astoria Gas tunnel 
being built in this way. 

It may be noted here that, although the shield has been 
used in the past very greatly for subaqueous work it is not 
necessarily confined to such situations, but may be used in per- 
fectly dry ground which, by any other system of excavation, 
would require timbering. Many miles of shield driven tunnel 
have been bored in the perfectly dry clay under London at a 
speed far greater than possible by any other method and on the 
Hudson & Manhattan Railroad, a large portion of the tube 
tunnels under streets and lands in New York and Jersey City 
were constructed with shields. 

TUNNELING SHIELDS 

The tunneling shield is the invention of Sir Marc Isambard 
Brunei, and was patented in Great Britain in 1818.* See 
Figure 113. This was circular in cross-section and embodied 
many of the features of the modern shield, although the shield 
used in the construction of the Thames tunnel was rectangular 
in section made up of a number of sections, each capable of being 
advanced independently. See Figure 114. Following this in 
1864, Barlow in England and Beach in the United States, ob- 
tained patents on shields. In 1869 the Tower footway tunnel 
was constructed in London with the use of a shield and cast-iron 
lining and it was this use of a metalHc Hning with a shield which 
has led to the great development in soft ground tunneling. In 
the year 1879 compressed air was first used in tunnel construc- 
tion at two places, the Hudson River tunnel in New York and a 
small tunnel in Antwerp. 

The construction of tube tunnels on a large scale for city 
passenger transportation, starting in London in 1886, led to the 
rapid development of the tunneling shield. This was followed 
by the introduction of the shield into the Hudson River tunnel 
in 1889 since which time shields in large numbers have been 
used in New York, Boston and other places in the United States. 



* British Patent No. 4204 of 1818. 



546 



MODERN TUNNELING 




SUBAQUEOUS TUNNELS 



547 



The shield consists of a cylinder made up of several thick- 
nesses of steel plates, within the protection of which the exca- 




SCALE OF FEET 

4 5 6 7 



Fig. 114. Vertical section of Thames tunnel shield; Brunei's design. 



vation is made and the tunnel lining is erected. See Figure 
lis- 



548 



MODERN TUNNELING 



Longitudinally the shield is generally divided into two parts 
by a diaphragm fitted with doors. 



ISlJg 




HALF SECTION A-B 



HALF SECTION C-D 



HORIZONTAL SECTION D 



Fig. 115. Tunneling shield used for Hudson River tunnels of Pennsylvania 
Railroad at New York. 



In the kinds of ground which are more or less self-supporting, 
either with or without the action of air pressure, it is necessary 
for the excavation to be removed in front of the diaphragm. 
The erection of the lining is invariably done behind the dia- 



SUBAQUEOUS TUNNELS 549 

phragm. The extent to which the excavation may be carried 
out freely in front of the diaphragm depends on many things — 
not the least of which is the diameter of the tunnel especially 
when being built under air pressure. If compressed air is being 
employed in the tunnel, it can be adjusted only to balance a 
certain head of water and in any open ground it is impossible 
to balance the water pressure at the invert without carrying 
so much excess pressure at the roof that the air will blow through 
the ground, thus leading to loss of air pressure and consequent 
flooding of the tunnel. It is therefore necessary to compromise, 
using a pressure equal to that at, say, half-way down the face 
so that there will usually be flowing water and ground on the 
lower half. This may entail very cautious work on the face 
with only very small areas exposed at a time and complete 
breasting of the entire face and sides so that the shield is shoved 
each time into a completely timbered and sheeted chamber, the 
space to be occupied by the advancing cutting edge having been 
excavated and refilled with mud, clay or other material into 
which the shield will penetrate. In other cases where the ground 
is close and dense and does not permit the escape of air or the 
influx of water the miners may go in front and excavate freely 
for the next shove with Uttle or no timbering or other safe- 
guards. 

In ground of the softest kind, the most notable example of 
which is the silt of the Hudson River, no excavation is done by 
hand in front of the diaphragm, but the shield is shoved bodily 
through the silt, either with all doors closed taking in no ground 
or with one or more doors partly opened so that a portion of the 
ground flows through the openings into the tunnel, where it is 
loaded into cars and taken out. Quite often a shield for a sub- 
aqueous tunnel which will pass through mud or gravel for most 
of its journey will have to be started in a full face of rock. This 
rock has to be taken out by drilHng and blasting so that a com- 
pletely clear passage is left for the shield. It is usual in such 
cases to drive at least a bottom heading in front of the shield in 
which a concrete bed or cradle shaped to the invert of the shield 
is laid, so that no damage may come to the cutting edge. 



550 MODERN TUNNELING 

The shield is ill adapted for rock work, and tunneling through 
rock with a shield is slow and expensive. 

The earliest work in which roqk was blasted in the invert 
ahead of the operation of the shield and under air pressure was 
in the Ravens wood Gas Tunnel under the East River at New 
York. At a somewhat later date, this was extensively done 
in the Hudson River Tunnels of H. & M. R. R., as well, as in 
the Pennsylvania tunnels and in the subway tunnels of the City 
of New York. Such blasting has to be exclusively ''pin blasting, ' ' 
using small holes and extremely light charges, as the soft ground 
overlying the rock must first be mined out and timbered, while 
the process of drilling and blasting proceeds in the removal of 
the rock bit by bit. 

The excavators work in advance of the diaphragm, passing 
the material through the doors and the erectors of the lining 
work in rear of same. The front end of the skin of the shield is 
protected by a cast-steel cutting edge, and the space in front of 
the diaphragm is generally divided into compartments partly to 
protect the men and partly to strengthen the shield. The shield 
is advanced by hydraulic rams, the cyhnders of which are placed 
in pockets or recesses in the diaphragm, the rams thrusting 
against the lining previously erected. 

The small annular space left between the outside of the Kning 
and the outside of the shield, as the latter advances, is filled with 
cement grout, gravel or both, or with unslaked lime which after 
injection swells up and fills the voids without setting hard for a 
considerable period. 

The general features of a typical shield are indicated in 
Figures ii6 and 117. 

Shield Equipment 

The equipment of the shield varies with the characteristics 
of the material through which the tunnel is being driven. In a 
stiff and reHable soil the diaphragm is reduced to its simplest 
terms and made as open as possible. The design of the doors in 
the diaphragm, must be made to suit the special needs of each 
case. The doors sometimes are hinged at the side, and some- 



SUBAQUEOUS TUNNELS 



551 



times at the top, and sliding doors have also been used. What 
has been proved to be a useful t^^e of door is one where the 
opening is closed by slats each one of which can be removed 
independently of the others. 



' m 






' ■ .^^^^ s^^^WWHIHF^ : 


^ ■ . .L... . . c^'i^^p^. ,' . -.ai ..*,fe— 


■1 ■ < '■ 

) 


'oc^,^T i ^^^^^■^^^'''^^'^wm^ *W 


'4^^^^^^^^'. ^ 


f -i^^Bp 



Fig. 116. Shield of Pennsylvania Railroad tunnels under Hudson River, 

New York. 



The earlier shields were advanced by screw jacks reacting 
against the completed lining, but this was soon abandoned for 
hydraulic rams, the power being supplied by a hydrauHc pump, 
either attached to the shield or in the main power house from 
which it is piped to the shield. In order to control the direction 
of movement of the shield the valves admitting the pressure are 
generally concentrated in several groups on the shield so that 



552 



MODERN TUNNELING 



the force can be increased, or diminished, on one side or the other 
the top or the bottom. The hydrauHc pressure used varies 
from 2000 to 5000 pounds per square inch and is usually supphed 
from hydrauHc pumps at the surface plant transmitted by 
hydrauHc pipe of steel to near the face. The flexible connections 
between the main and the moving shield are made up with heavy, 
small-size copper tubing. 




Fig. 117. 



Shield of Hudson & Manhattan Railroad under Hudson River, 
New York. 



The rams react against the previously erected tunnel lining. 
With a cast-iron lining in order to avoid damage to the flanges, 
the head of the ram is offset '' "| " shaped so as to bear against 
the axis of the skin of the iron instead of on the flange, thus 
reducing the danger of breakage of flanges but introducing 
occasional bending of the rams. 

In a concrete-Hned tunnel it is usual to embed steel or iron 
members in the concrete to take this thrust. 

Practically aU shields for railway tunnels are equipped with a 
revolving crane or erector to pick up and place in position the 
lining segments. Frequently the erector is not attached to the 



SUBAQUEOUS TUNNELS 553 

shield but is supported by temporary brackets attached to the 
Uning at the sides at about the level of the axis of the tunnel. 

In suitable material various types of excavating and loading 
machinery have been attached to the shield. In some places 
rock is encountered at varying heights with soft material above. 
In such cases the shields are pro\^ded with fixed or movable 
sliding platforms to furnish protection by an overhead cover 
from the soft material to the miners while drilling the rock. 

Some material is so unstable as to require breast-boarding 
of the face which must be supported continually, excepting for 
the width of a board at a time, and some shields are equipped 
with devices to support the face while this is being done and the 
shield is being advanced. Wliere this is not done the face is 
supported by bracing from the shield as the excavation progresses. 
To permit the advance of the shield, this bracing is transferred 
to struts passing through the shield doors, or through openings 
in the shield diaphragm provided for the purpose, bearing on 
a cross-beam reacting against the lining as indicated in Figure 1 18. 

Wood Lining 
In the approach tubes to the Detroit River Tunnels as well 
as in the Dorchester Tunnel at Boston, and elsewhere, a lining 
has been sucessfully employed in conjunction with a shield, using, 
instead of iron plates, segmental blocks of w^ood breaking joints 
and dowelled to each other, making up an exterior lining of soHd 
wood from 8 to lo inches thick, inside which is afterwards 
placed a permanent backing of concrete. 

Roof Shields 
In suitable material roof shields have been used at various 
places. The procedure on the Boston subway, which was com- 
structed in a stifif clay, w^as to excavate two narrow headings on 
the line of each sidewall, then to construct the sidewalls of 
concrete, laying a channel bar as a track for the shield on top 
of each sidewall and then advance the roof shield which ran 
on rollers on the channel bar track. As the arch was also con- 
structed of concrete, metal struts were embedded in same to 



554 



MODERN TUNNELING 



avoid damage from the thrust of the rams. After the construc- 
tion of the arch the centra] core in the lower half of the section 




Fig. ii8. Vertical section through tunnel and shield showing face breasted 
and strutted through the shield while shoving. 

was excavated and the invert constructed, thus completing the 
section. Figure 119. 

CAISSON METHOD 

Another method of building a subaqueous river crossing is 
to make the passage inside a succession of caissons sunk into 
the bed of the stream. This method was used in one of the river 
crossings of the Seine by the Metropolitan Railway in Paris. 
The two arms of the river were crossed by five caissons 66 feet 



SUBAQUEOUS TUNNELS 



555 



to 142 feet long sunk separately and joined together after being 
in position. These caissons were made of structural steel and 




concrete, an internal lining of cast-iron plates being added after 
the caissons were in position. In this case the method proved 



556 



MODERN TUNNELING 




-s 



3 -O 







SUBAQUEOUS TUNNELS 557 

to be very expensive and slow the only advantage being that 
the rail level was placed at a higher plane than would have been 
possible by driven tunnehng * (Figure 120). 

Reinforced concrete caissons were also used by the Hudson 
& Manhattan Railroad in Jersey City as short sections of the 
tunnel structure, in constructing enlargements for switches at 
junctions in Jersey City. These were of a simpler and more 
economical construction.! 

Another method which also enables the rails to be placed on 
a higher plane was that followed by the crossing of the Detroit 
River at Detroit by the Michigan Central Railroad. The 
method was to dredge a trench in the bed of the river, into which 
a steel box-shaped form, in the center of which was a steel tube 
riveted and caulked watertight, w^as sunk in sections and around 
which concrete was deposited through tremies. These sections 
were joined together, unwatered and an interior concrete lining 
placed, the approaches being constructed with a shield. { 

COFFERDAM METHODS 

Several tunnels have been constructed across the Chicago 
River by enclosing a portion of the stream at a time, between 
cofferdams within which, after unwatering, the excavation was 
made and the structure built. A variation of this method was 
used in the construction of the first New York subway under the 
Harlem River. This involved the closing of half of the river 
to navigation at a time, the dredging of a trench to a little below 
the springing line of the arch and the driving of sheet piling on 
the sides. This piling was cut off at the springing line. The 
upper half of the tunnel was constructed on floating supports 
above the surface of the water and then lowered to a bearing on 
the sheet piles and intermediate temporary piles, after which 

* "Les Travaux Chemin de Fer Metropolitain Municipal de Paris a la 
traversee de La Seine," by L. Biette, Paris. 1910 Dunod et Pinat. 

t " The Hudson River Tunnel of the Hudson & Manhattan R. R. Co.," 
by Chas. M. Jacobs, Minutes of Proc. Inst. C. E., Vol. CLXXXI. 

t Trans. Am. Soc. C. E., Vol. LXXIV, p. 288, by Wilson S. Kinnear and 
Minutes of Proc. Inst. C. E., Vol. CLXXXV, p. 2, by William J. Wilgus. 



558 MODERN TUNNELING 

air pressure was installed, the tunnel unwatered, the excavation 
completed and the lower portion of the tunnel constructed in 
place.* 

In the construction of the four-track crossings of the Harlem 
River by the Lexington Avenue subway, similar methods to 
those used in Detroit were followed. 



CONSTRUCTION PLANT 

For subaqueous tunneling the first essential is compressed 
air for the working headings, generally not exceeding 50 pounds 
per square inch pressure, and at a higher pressure up to say 150 
pounds for the operation of drills and machinery of all sorts. 
This apparently high pressure has to be carried as the exhaust is 
into the working chamber which thereby acts as back pressure 
on the drills or machines. Electricity is also used for lighting 
and is often also used for haulage, hoisting and the operation of 
machinery of all kinds. 

BOILERS 

The capacity of the boilers is naturally dependent on whether 
or not the power for constructing the tunnel is obtained from 
steam or by electricity for producing compressed air. Sufficient 
power must be provided for supplying the compressed air in 
the tunnel itself and for rock drills, haulage, hoisting, lighting, 
pumping and operating tools of all kinds. For a railway tunnel 
under average conditions from 500 to 1000 boiler horse power 
per heading should be sufficient. This should be provided in 
convenient units with some reserve capacity so that one boiler 
can cut out at a time for cleaning or repairs. With the boilers, 
the auxiliaries such as feed pumps, condenser plant, circulating 
water pumps must be considered, and provision for storage and 
handling coal and ashes must be made. 



Trans. Am. Soc. C. E., Vol. LXXVIII, p. 252. 
Engineering News, Vol. 72, p. 1250. 



SUBAQUEOUS TUNNELS 559 

COMPRESSED AIR 

The amount of low-pressure air required depends on the 
porous character of the soil. For a railway tunnel from 2000 to 
4000 cubic feet per minute of free air per heading is provided. 

The amount of high-pressure air required depends upon the 
number of drills or other machinery to be operated in that way. 

The most authoritative figures on requirements for com- 
pressed air for carrying on pneumatic tunnel construction are 
contained in the specifications under which the Pennsylvania 
Railroad, Hudson and East River Tunnels and the tunnels of 
the Public Service Commission (New York City) have been 
constructed. Practically an air pressure of 50 pounds per 
square inch above normal atmosphere constitutes the limit 
at which labor can carry on the construction of works of this 
character. 

The Pennsylvania specifications provide for tunnels driven 
with shields under compressed air, that the contractor must 
provide at each shaft an adequate plant of boilers, air compres- 
sors, hydraulic machinery, electric generators, and all necessary 
plant, with a reasonable duplication to meet unusual and 
unexpected emergencies. 

Compressors to be of sufficient capacity to dehver regularly 
into each heading at least 300,000 cubic feet of free air per hour 
at a pressure of 50 pounds per square inch above normal atmos- 
phere, and for a larger amount if found necessary during the 
progress of the work. Air for the compressors must be drawn 
from the exterior of the power house and the intake so located 
as to give pure cool air. The air shall be further cooled and 
oil and other impurities removed as completely as practicable 
before delivering into the headings. 

In order to provide a reasonable margin for repairs and con- 
tingencies a spare compressor and boiler plant shall be provided 
at the shaft, and kept in good condition and repair ready for 
immediate use. The capacity of the spare plant shall be 25 per 
cent, of that required in the preceding paragraph for regular 
operation. 



560 MODERN TUNNELING 

The air shall be dehvered into each heading through two 
supply pipes of such capacity that the velocity of air through 
them, in regular working shall not exceed 40 feet per second. 

A foul air vent pipe 8 inches in diameter shall be carried 
back from the shield through each lock bulkhead to the outer 
atmosphere to ventilate the heading, and shall be provided with 
a lo-inch regulating valve near the shield to maintain the pres- 
sure required. 

Bulkheads to be built in each tunnel at intervals not to 
exceed 1000 feet and there shall, at no time, be an interval of 
more than 1000 feet between a shield and the bulkhead nearest 
to it. Each bulkhead shall be provided with two air locks near 
the bottom at least 6 feet in diameter and 20 feet long for the 
passage of men and materials, one near the roof as an emergency 
lock for the passage of men only, and one pipe lock 12 inches in 
diameter and 31 feet long with a gate valve for passing pipes, 
rails, etc. 

The specifications of the Public Service Commission simi- 
larly provide for complete and adequate plant, indicating a 
preference, however, to the operation of the air compressing 
machines by electricity which could be advantageously pur- 
chased from public central station supply at reasonable rates. 

The specific requirements are as follows: 

"The air-compressing plant shall be capable of furnishing simu- 
taneously to each heading an air supply sufficient in volume and pres- 
sure to enable work to be done as nearly as possible in the dry and 
to afford the degree of ventilation hereinafter specified, including to 
each heading where a shield is used an air supply at a pressure of 
forty-five (45) pounds per square inch above atmospheric pressure 
equal to at least 10,000 cubic feet of free air per minute as measured 
by piston displacement at a piston speed for any machine not exceed- 
ing the speed corresponding to the safe working capacity of such 
machine." 

The specifications require continuous record of the operation of 
all compressors and the equipment of cooling apparatus for cooling 
the air supplied to the tunnels. 

These specifications require that if the air furnished in the 
headings exceed 22 pounds per square inch above atmospheric 



SUBAQUEOUS TUNNELS 561 

conditions, two stages of air pressure shall be used, and further 
that the distance from the heading to the next bulkhead shall 
not exceed 800 feet, and that there shall be provided two main 
operating locks and also an emergency lock. The air to be 
supphed to the headings to be by two pipes, each at least 10 
inches in diameter. 

It is further provided as follows : 

''The supply of fresh air to the tunnel shall be sufficient to per- 
mit work without danger or discomfort; and where work is in com- 
pressed air, such supply shall be sufficient at all times and places to 
prevent the accumulation of carbon dioxide to a greater amount than 
one (i) part in a thousand (1000) by volume." 

In the State of New York, due to the great amount of air 
pressure tunnel work which has been executed, the Legislature 
enacted legal requirements in respect of the operation of employ- 
ment of labor under varying degrees of air pressure and by Act 
(Chapter 36 of Laws of 1909 as amended to July, i, 191 7) 
provided for other matters relating to the operation under air 
pressure. Briefly the requirements in respect of the duration of 
employment is as follows: 

Between normal and 21 pounds pressure per square inch, 

8 hours in 24 with interval of at least 30 minutes. 
Between 22 pounds and 30 pounds, 

6 hours in 24 with division in two periods of 3 hours each with 
at least i hour interval between each such period. 
Between 30 pounds and 35 pounds, 

4 hours in 24 with division in two periods of 2 hours each with 
at least 2 hours interval between each such period. 
Between 35 and 40 pounds, 

3 hours in 24 divided into periods of not more than i^ hour 
each, with intervals of 3 hours between each such period. 
Between 40 pounds and 45 pounds, 

2 hours in 24 divided into periods of not more than i hour 
each, with interval of at least 4 hours between each such 
period. 
Between 45 pounds and 50 pounds, 

Not more than 90 minutes in 24 hours, divided into periods of 
45 minutes each, with an interval of 5 hours between each 
such period. 



562 MODERN TUNNELING 

AIR LOCKS 

In order to install air pressure on the working face of a tun- 
nel, it is necessary to build a bulkhead wall across the tunnel to 
restrain the compressed air, and in order to obtain access to the 
working face, air locks for both materials and men are provided 
in these bulkheads. These air locks are merely cylinders of 
steel plate with doors in each end, opening against the pressure 
side, and having valves inside and outside for equalizing the 
pressure. A construction track is laid through the center and 
a bench along each side. A plate glass ''bulls eye" is placed 
in each door. 

The main materials locks are set up so that the tracks through 
the locks are on the same level as the main operating construc- 
tion tracks in the tunnels. This means that the main locks are 
low down in the tunnel section and are side by side. The usual 
size of these locks is from 6 feet to 7 feet diameter and about 
20 feet long. A small sized man-lock called also an emergency 
lock is usually installed as near as possible to roof grade. Timber- 
lock at the side above track grade is usually a pipe 18 inches 
diameter, by 31 feet long, with gate valves at both ends. The 
concrete setting for these locks varies in thickness according to 
pressure carried and diameter of tunnel, but commonly 5 feet 
to 12 feet thick. The purpose of locating the man-lock at roof 
grade is to provide safety for workmen in the event the workings 
are partially flooded and the lower locks are inaccessible, escape 
is then provided at a higher level. 

When a considerable length of tunnel has been built it is the 
practice to install a second or third set of locks and the full 
pressure is only used in the forward lock and the men pass 
through the intermediate stages at a reduced pressure. This 
has been found to diminish the occurrence of compressed air 
illness. 

ELECTRICITY 

The underground workings are lighted by electricity, and as 
work is generally carried on throughout the 24 hours, they are 
also needed on the surface at night, If any electrically operated 



SUBAQUEOUS TUNNELS 563 

machinery is to be used this must be included in the estimate of 
the amount of electricity to be generated. If there is a rehable 
source of electricity available it is commonly purchased and if 
not it must be generated in the power plant. 



HYDRAULIC POWER 

The operation of the shields by hydraulic power and the use 
of hydrauUc power, also, in many designs of erectors for the 
erection of the plate lining, necessitates the installation of a 
hydrauhc power plant carrying a working pressure of from 5000 
to 6000 pounds per square inch. It is usual to generate the 
hydrauhc power for these purposes at the tunnel power plant 
on the surface as thereby the care and maintenance of the 
machinery can be looked after much better. Water under pres- 
sure is conveyed through the tunnels to the shield in extra 
heavy hydrauhc pipe carried continuously through the lock 
bulkheads and maintained as near as possible to the face. In 
some cases the hydrauhc pumps are installed in the tunnels and 
moved along as the shield advances, this being done in order to 
save the cost of the hydrauhc pipe for the entire lengths of the 
tunnels, but is generally not as advantageous, as particularly 
with the high pressure carried, the friction loss in the hydrauUc 
pipe is very small. The usual type of pump used for this 
purpose is a steam operated geared pump with a heavy fly- 
wheel, which equalizes advantageously the load factor of the 
machine. At the same time the pumps are frequently driven 
by electric or other power depending upon the source of 
power used in the plant installation. The pumps are only 
operated when power is needed at the face, upon notice given 
to the engine-room by telephone from the superintendent in 
charge of the operations at the shield. An accumulator should 
always be used in the hydrauhc circuit, both to provide storage 
capacity and to give smooth action in the operation ot the 
hydraulic machinery. 



564 MODERN TUNNELING 

MISCELLANEOUS PLANT 
Plant is also needed for the conveying and removal of the 
excavated material and for the handling and erection of the 
tunnel lining and materials built into the tunnel, but as this 
problem does not differ materially in subaqueous tunnels from 
others, no special description is necessary. Endless wire rope 
haulage has been the most successful in general use for this 
purpose. 

COST OF SUBAQUEOUS TUNNELS 
Shield Driven Iron Lined 

Any attempt to state the cost of the various types of sub- 
aqueous tunnels would be of practically no value as a guide to 
the probable cost of any other work. There are comparatively 
few works of this character which have been executed in the 
United States, or elsewhere, and there is such tremendous vari- 
ation in the conditions in all of these cases, that little can be 
learned from the cost of one undertaking to enable us to know 
what is likely to be the cost of others under different conditions 
and surroundings. 

Taken generally, the production of subaqueous tunnels 
represents one of the most costly works the civil engineer is 
likely to undertake. Labor conditions are constantly changing 
and the tendency of Legislatures to enact laws governing the 
conditions of labor on this class of work, makes it particularly 
difficult to anticipate what the conditions will be under which 
any work may be carried out. 

Under pre-war conditions, the cost of iron plates for tunnel 
construction varied from $26 to $30 per 2000 pounds ton, 
delivered New York. These prices being based on No. 2 
Foundry pig iron, averaging approximately $16 a ton. Under 
present conditions of transportation, labor and price of pig iron, 
it is difficult to foresee what the cost will be. 

The following table shows the approximate cost per cubic 
foot of volume excavated for several subaqueous shield-driven 
tunnels. These figures are obtained by dividing the total con- 



SUBAQUEOUS TUNNELS 



565 



tract price for each tumiel by the total number of cubic feet 
of tunnel displacement. There is thus obtained an average 
price per cubic foot of volume and this average price includes 
all the work incidental to the production of the complete tunnel 
structure, excluding the track or roadway, and including the 
shafts or other works of access, the plant, permanent materials, 
temporary materials, labor, suppHes, all miscellaneous expenses 
and profit to the contractor. 



Date 



Name of Tunnel 



Diameier 
Outside 



Approx. 
Cost per 
Cubic Ft. 



1892 
I 904- I 909 
I 904- I 909 
I 904- I 909 
I 903- I 909 

1914-1918 
1914-I918 
1916-1918 
1916-1919 

I921-1924 



Blackwall, River Thames, England 

Rotherhithe, River Thames, England 

Pennsylvania R.R,, Hudson River, N. Y. . . . 

Pennsylvania R.R., East River, N. Y 

Hudson & Manhattan R.R., Hudson River, 

New York 

N. Y. Rapid Transit, East River (Sand) 

N. Y. Rapid Transit, East River (Sand) 

N. Y. Rapid Transit, East River (Sand) 

N. Y. Rapid Transit, East River (For larger 

part in solid rock) 

N. Y. Vehicular Tunnel, Hudson River, N. Y . 



27.0 
30.0 
23.0 
23.0 

16' 7" 
18' o" 
18' o" 
18' o" 

18' o" 
29' o" 



$1.10 

1.08 
1.62 
1-73 

1-65 
2.15 
1-93 
1.94 

1-55 
3.60* 



Estimated. 



While the figures stated above, as cost of shield -driven, iron- 
lined tunnels, are approximate only, they nevertheless reflect 
the influence of rapidity of progress in construction. The tun- 
nels under the Hudson (or North) River were excavated in silt 
or in part rock and part silt. In silt the progress is extremely 
rapid; the Hudson & Manhattan R. R. ha\dng excavated and 
lined as much as 72 feet of full-sized tunnel in a single day and 
from one working point. The work in a mixed face of rock 
and silt is on the other hand extremely slow, the progress often 
not yielding more than 2 feet per day. The average rate of 
progress between end points is the governing factor in cost. 
It will readily be seen that while the cost of hning in place is 
practically a fixed rate per lineal foot of tunnel, the cost of oper- 



566 MODERN TUNNELING 

ating the plant and the labor employed both in the tunnel and 
on the surface is more or less constant per diem irrespective of 
advance. The rate of progress in the sands, gravels and glacial 
formations under the East River indicate the greater cost on 
account of the generally slower average rate of advance. 

When a tunnel shield is progressing in silt the labor cost per 
foot of tunnel becomes very small (less than $20 per foot). 
Under these conditions cost of lining bears a very large propor- 
tion of total cost of tunnel and other costs line up approximately 
as proportions of the total per foot cost. 

Cast-iron lining 54 per cent. 

Labor 22 per cent. 

Fuel, supplies and overhead 24 per cent. 

On the other hand when progress is retarded by rock or bad 
materials or other interferences these figures change tomore nearly: 

Cast-iron lining 40 per cent, per foot cost 

Labor 40 per cent. 

Fuel, supplies, etc 20 per cent. 

These figures are irrespective of the cost of internal lining of 
concrete which may be executed subsequently. 

TRENCH TYPE COST 

As to the cost of various types of caisson and trench tunnels 
there is little information of value. 

The Harlem River subway, for which a contract was awarded 
in 191 2, included a four-track structure for rapid transit rolling 
stock equipment. It was awarded to the contractor at a price 
of $375 per linear foot of track. The depth of water in the chan- 
nel way was 26 feet and the distance between bulkhead lines 
was 600 feet. The river bed consisted of sand and gravel over- 
laid with about 6 feet of mud. The velocity of current in the 
water-way was about i mile per hour. 

Similar sized iron-lined tunnels were later awarded for con- 
struction under the East River at much greater depths, and in 
more difficult operating conditions at prices varying between 
$390 and $420 per foot. 

The Detroit River Tunnel, described elsewhere, was designed 



SUBAQUEOUS TUNNELS 567 

for double-track main-line steam railroad equipment, on which 
the subaqueous section, which was that portion sunk in trench 
and completed with tremie concrete, cost $1,772,444. This would 
represent a net cost of approximately 48 cents per cubic foot of 
external displacement of structure or $331.50 per foot of track. 

These two works represent practically the only tunnels of 
this type which have been constructed in the United States. 
A tunnel of a somewhat similar character, previously referred 
to, was built under the Seine in Paris at a very great expense, 
the work extending over an unprecedented period. 

The real advantage presented by this mode of construction 
lies in the possibility of keeping the elevation of the tunnel at 
a higher plane than would be the case with a driven tunnel, 
since the question of adequate earth cover during the construc- 
tion period does not enter in the case of a trench tunnel. By 
this means the approach gradients may be shortened or made 
less severe and the operating conditions thereby improved. 

It will be realized that, within the limits of these four chapters, 
it has been impossible to do more than touch on the most salient 
features of such a wide subject as railroad tunneling. 

A fairly full bibhography, confined to the English language, 
is appended. This includes papers read before Engineering 
Societies and articles which have appeared in the technical 
journals, mostly between the years 1910 and 1920, but including 
also a few papers and articles prior to that period dealing with 
certain outstanding pieces of work. It also includes several 
books on the subject. 

The title of each paper, article or books gives, as a rule, an 
indication of the specific part of the general subject which it 
covers and readers who desire to go more fully into the details 
of the matter are referred to the bibliography. 

It may be stated, particularly for the benefit of those who 
may not be able to reach any public library, that the Engineer- 
ing Societies Library will furnish, at a small charge, photostat 
copies of any paper or article desired. Requests for this service 
should be addressed to the Director, Engineering Societies 
Library, 29 West 39th Street, New York. 



BIBLIOGRAPHY TO CHAPTERS XVIII-XXII 

Papers in Engineering Societies and articles in the technical journals. 

Note. — For the most part, the papers and articles listed are those which 
have appeared during the last ten years, 1910 to 1919 inclusive. A few impor- 
tant papers prior in date to this have been included and one or two of the year 
1920. 

Only articles and books in the English language have been listed. 

The list does not profess to be exhaustive but it is believed that the field 
is well covered. 

1895. — "The City and South London Railway (London) with 
Some Remarks on Subaqueous Tunneling by Shield and 
Compressed Air." J. H. Greathhead. Min. Proc. Inst. 
C. E,, Vol. CXXIII, p. 39. 

1896.— "Iron Tunnels." W. O. Leitch. Min. Proc. Inst. C. E., 
Vol. CXXV, p. 377. 

1897. — "The Blackwall Highway Tunnel. The River Thames, 
London." D. Hay and M. Fitzmaurice. Min. Proc. 
Inst. C. E., Vol CXXX, p. 50. 

1902. — "The Greenwich Footway Tunnel" (London). W. C. 
Copper thwaite. Min. Proc. Inst. C. E., Vol. CL, p. i. 
"Subaqueous Tunneling through Thames Gravel. The 
Baker Street and Waterloo Railway." A. H. Haigh. 
Min. Proc. Inst. C. E., Vol. CL, p. 25. 

1904.— "The Ventilation of Tunnels." Chas. S. Churchill. 
Trans. Am. Soc. C. E., Vol. LIV, Part C, p. 525. 
"The Ventilation of Tunnels." F. Fox. Trans. Am. Soc. 
C. £., Vol. LIV, Part C, p. 553. 

1906. — "The Scranton Tunnel of the Lackawanna & Wyoming 
Valley R. R." G. B. Francis and W. F. Dennis. Trans. 
Am. Soc. C. £., Vol. LVI, p. 219. 

.508 



BIBLIOGRAPHY 569 

1907. — ''The Simplon Tunnel " (Switzerland and Italy). F. 
Fox. Min. Proc. Inst. C. £., Vol. CLXVIII, p. 6i. 

1908. — ''The Rotherhithe Highway Tunnel" (River Thames, 
London). E. H. Tabor. Min. Proc. Inst. C. E. (London), 
Vol. CLXXV, p. 190. 

"The New York Rapid Transit Subway." Wm. Barclay 
Parsons. Proc. Inst. C. E., Vol. CLXXIII, 1907-1908, 
part 3. 

1909. — "Caisson Disease and its Prevention." H. Japp. 
Trans. Am. Soc. C. E., Vol. LXV, p. i. 
"Cwm Cerwyn Tunnel, Port Talbot, Wales. Relining a 
Portion of This Railway Tunnel." By W. Cleaver. Min. 
Proc. Inst. C. E., Vol. CLXXXVIII, p. 380. 
"Construction of the Tunnel System of the Hudson & 
Manhattan Railroad Company." J. V. Davies. Ry. Age 
Gaz., 1909, Sept. 17, 24; Oct. i, 8, 15, and 22. 

1910.— ''New York Tunnel Extension of the Pennsylvania R. R." 
Trans. Am. Soc. C. E., Vol. LXVHI, Sept., 19 10. 
"The North River Division." Charles M. Jacobs. 
"The East River Division." Alfred Noble. 
"The Bergen Hill Tunnels." F. Lavis. 
"The North River Tunnels." B. H. M. Hewett and 
W. L. Brown. 

"The Crosstown Tunnels." J. H. Brace and F. Mason. 
"The East River Tunnels." J. H. Brace, F. Mason and 
S. H. Woodard. 

"The Contractors' Plant for East River Tunnel." H. Japp. 
Trans. Am. Soc. C. £., Vol. LXIX, Oct., 1910. 
"Some Features of the Alignment Work on the Pennsyl- 
vania Tunnels." F. Mason. Harvard Eng. Jour., Apr., 
1910. 

"Subaqueous Section of the Detroit River Turmel." Eng. 
Rec, Dec. 18, 1909, serial, ist part. 



570 MODERN TUNNELING 

''The Bergen Hill Four-track Tunnel." Eng. Rec, Dec. 

i8, 1909. 

''Engineering Features of Detroit River Tunnel." Ry. 

Age Gaz., Apr. 29, 1910. 

"The Tunnel Construction of the Hudson & Manhattan 

R. R. Co. J. V. Davies. Proc. Am. Philosoph. Soc, Vol. 

XLIX, No. 195, 1910. 

"Construction of Rapid Transit Railroad in Relation to 

the Handling of Passengers as Illustrated by the Hudson 

& Manhattan R. R." J. V. Davies. Proc. Eng. Club of 

Philadelphia, Vol. XXVII, No. 4, Oct., 1910. 

191 1.—" Tunnel-Driving in the Alps." W. L. Saunders. Bull. 
Inst, of Min. Eng., July, 191 1. 

"Driving Spiral Tunnels on the Canadian Pacific Ry." 
Eng. News, Nov. 10, 1910. 

"Hudson River Tunnels of the Hudson & Manhattan 
R. R." Charles M. Jacobs. Minutes of Proc. Inst, of 
C. E., Vol. CLXXXI, 1909-1910, Part 3. 
"Rebuilding La Salle Street Tunnel, Chicago." Eng. 
News, Jan. 12, 191 1. 

"The Transandine Summit Tunnel." John Pollack. Engng. 
(London), Dec. 30, 1910. 

"The Loetschberg Tunnel." E. L. Corthell. Eng. News, 
Jan. 5, 1911. 

"The Detroit River Tunnel." W. S. Kinnear. Trans. 
Am. Soc. C. E., Vol. LXXIV, Dec, 1911. 

1912. — "Notes on a Tunnel Survey." F. C. Noble. Proc. Am. 
Soc. C. E., Dec, 1911. 

"Discussion on Above." Pro. Am. Soc. C. E., March, 191 2, 
and Apr., 1912. 

"The Detroit River Tunnel." W. J. Wilgus. Min. Proc. 
Inst, of C.E., Vol. CLXXXV, 1910-1911, Part 3. 
"Subaqueous Tunneling." H. Japp. Proc. Eng. Club of 
Philadelphia, July, 191 2. 



BIBLIOGRAPHY 571 

"Air Resistance to Trains in Tube Tunnels." J. V. Davies. 
Proc. Am. Soc. C. E., Apr., 191 2. 

''Methods of Construction-Sand Patch Tunnel B. & O. 
R. R." Engng. Contng., June 26, 191 2. 

"The Concorde Tunnel of Paris MetropoHtan Ry." P. 
Seurot. Proc. Inst. C. £., Vol. CLXXXVIII, 1912, 
Part 2. 

"Seepage in Subaqueous Railroad Tunnels." Eng. Rec, 
Aug. 31, 1912. 

"Ventilating Equipment of the Pennsylvania Tunnels at 
New York." B. W. Bennett. Eiig. Rec, June 8, 191 2. 

"West Shore Weehawken Tunnel Ventilation." Ry. Age 
Gaz., Aug. 9, 191 2. 

"The Sanitation of Construction Camps." H. F. Gray. 
Trans. Am. Soc. C. E., Vol. LXXVI, p. 493. 

"Paris Metropolitan Railway Concorde Tunnel across the 
Seine River." P. Seurot. Min. Proc. Inst. C. E. Vol. 
CLXXXVIII, p. 380. 

1913. — "Elimination of Timbering in Rock Tunneling." J. F. 
O'Rourke. Eng. News, Feb. 13, 1913. 

"Relining the Mauvages Tunnel on the Marne Ship Canal." 
F. B. Mann. Eng. Rec, Feb. 22, 1913. 

"Tunnel Relining on 18 Tunnels of the Virginian Pvy. 
under Traffic." Ry. Age Ga7-., June 20, 19 13. 

"Building a Four-tube Steel Tunnel in Sections." Iron 
Trade Rev., Sept. 25, 1913. 

"The Astoria Tunnel, East River, New York." H. Car- 
penter. Eng. News, Oct. 16, 1913. 

"Difficult Tunnel Work on the Metropolitan Railway in 
Paris." Eng. News, Sept. 11, 19 13. 

1914. — "Concrete Blocks for Tunnel Lining." Munic Jour., 
March 19, 1914. 



572 MODERN TUNNELING 

''Concrete-lined Highway Tunnel Carrying Heavy Loads 
from Railways above It. The Corliss Steel Tunnel, 
. Pittsburgh." Eng. Rec, Aug. 15, 1914. 

''Lining Long and Deeply Overlaid Tunnels." E. Lauchli. 
Eng. News, Aug. 6, 1914. 

"Lining Tunnels on the Grand Trunk Pacific in British 
Columbia." Eng. Rec, Aug. 8, 1914. 

"Problems in Driving Long and Deeply Overlaid Tunnels." 
E. Lauchli. Eng. Rec., Nov. 8, 1913. 

"Subway Tunnel, Harlem River, New York." Eng. Rec, 
Nov. 15, 1913. 

"Proposed Tunnel under EngHsh Channel." C. O. Burge. 
Eng. Rec, Nov. i, 19 13. 

"The World's Greatest Tunnels (Except Town Tunnels)." 
Engnr., London, Nov. 28, 19 13. 

"Construction Methods of Mont d'or Tunnel." Engng. 

Contng., Nov. 26, 1913. 

"The Four-mile Mont d'or Tunnel. French Jura. Heavy 
Water Flow in Firm Rock." Eng. News, Jan. 15, 1914. 

"Driving and Lining Point Defiance Tunnel with Poling 
Boards and Semicircular Shield." Eng. Rec, Feb. 7, 1914. 

"The Second Simplon Tunnel." Engnr., London, Feb. 13, 

1914. 

"Subaqueous Tunneling." P. Seurot. Trans. Soc Can. C. 

E., April 23, 1914. 

"Tunnel Ventilation during Construction." E. Lauchli. 
Canadian Eng., July 2, 19 14. 

"Whitehall Street Tunnel, New York. Cast-iron Tunnels 
Under the East River." Eng. Rec, July 25, 19 14. 

"Old Slip Tunnel, East River, New York." Eng. Rec, 
Aug. 22, 1914. 

"The Havens tein Tunnel, Switzerland." Engnr., London, 
July 24, 1914. 



BIBLIOGRAPHY 573 

1915. — "The Relation of Geology to Railway Tunnel Location." 
E. C. Eckel. Contract Rec. (Toronto), Oct. 28, 1914. 
"Tunneling and Geology." E. Lauchli. Canadian Eng., 
Sept. 16, 1915. 

"Lining Long Tunnels and Tunnels Subjected to Heavy or 
Eccentric Ground Pressure." E. Lauchli. Canadian Eng., 
Jan. 7, 1915. 

"Determination of Stresses in and Design of Cast-iron 
Lining for Subaqueous Tunnels." P. Seurot. Engng. 
Contng., Jan. 3, 1915- 

"The Ventilation of Allegheny Summit Tunnel, Virginian 
Ry." Gen. Elec. Rev., Dec, 1914. 

"The Astoria Tunnel, under the East River, New York." 
J. V. Davies. Trans. Am. Soc. C. E., Vol. LXXX, 1916. 

"Flooding and Recovery of the Astoria Tunnel." H. 
Carpenter. Eng. News, October 7, 191 5. 
"Extensions of the Hudson River Tunnel of the Hudson & 
Manhattan Railroad." J. V. Davies. Proc. Inst. C. £., 
Vol. CXCVn, Session 19 13 and 19 14, Part 3. 

"The Largest Tunnel in the World, 4 Miles Long, 72 ft. 
Wide, at Marseilles, France." Eng. News, Aug. 26, 191 5. 

"Piercing the Selkirk Mountain for a 5-mile Double- 
track Tunnel, Rogers Pass, B. C." Eng. Rec., Dec. 5, 1914. 

"The Snoqualmie Summit Tunnel, 11,886 Feet Long, 
Cascade Mountains." Eng. News, Feb. 18, 191 5. 

"The Stockton Tunnel, San Francisco. 50 Feet Wide." 
Engng. Contng., Feb. 3, 191 5. 

"Subaqueous Highway Tunnels." Geo. D. Snyder. Trans. 
Am. Soc. C. E., Vol. LXXVHI, p. 252. 

1916. — "Tunnel Drill Carriages." S. P. Brown. Eng. Rec, 
Jan. 8, 1916. 

"Tunnel Lining by Compressed Air Mixing and Placing." 
Engng. Contng., Jan. 12, 1916. 



574 MODERN TUNNELING 

''Nicholson Tunnel on D. L. & W. R. R. Brick-lined." 
Ry. Engng. and Main, of Way, Jan., 1916. 
"Construction Methods. Rogers Pass Tunnel." J. G. 
Sullivan. Can. Soc. C. £., Jan. 13, 1916. 
''Rapid Tunneling in Brazil." J. C. Balcomb. Eng. 
News, May 18, 1916. 

"The Laxaxalpam Aqueduct Tunnels, Mexico." J. Forgie. 
Proc. Inst. C. E., Vol. CC, 1914-1915, Part 2. 
"The City Tunnel of the Catskill Aqueduct, New York." 
W. E. Spear. Am. Water Works Assn. Jour., June, 1916. 
"The Construction of the Dorchester Tunnels under 
Fort Point Channel, Boston." A. A. Cohill. Boston Soc. 
of C. E. Jour., May, 191 6. 

"Needle Beam Heading Method in Dry Ground, Newark, 
N. J." Eng. Rec, Mar. 4, 1916. 

"Wall Plate Drift Method. Twin Peaks Tunnel, San Fran- 
cisco." Eng. Rec, Feb. 26, 1916. 

"Repairing a Tunnel Lining under Difficult Conditions. 
Concrete Atomizer Used by Chicago Great Western R. R. 
at Winston, 111." ^^3;. Age Gaz., Dec. 17, 191 5. 

"An Economic Comparison of European and American 
Methods of Tunnel Driving." E.Lauchh. Engng. Contng., 
Nov. 24, 1916. 

"Modern Methods of Railway Tunnel Construction." 
Chas. S. Churchill. Ry. Rev., October 30, 191 5. 

"East River Tunnel Shields, New York. Details of 18 Ft. 
Shields." Eng. News, Nov. 11, 191 5. 

"Construction Plant and Methods Employed in Concrete 
Lining and Double- track Railway Tunnel under Traffic." 
R. Meacham. Engng. Contng., Nov. 17, 191 5. 
"Completing the Mount Royal Tunnel into Montreal." 

Ry. Age Gaz., Nov. 5, 1915. 

"Methods Used in Building the Rogers Pass Tunnel." 

Eng. News, Nov. 11, 191 5. 



BIBLIOGRAPHY 575 

''Construction Progress on the Twin Peaks Tunnel, San 
Francisco." Eng. News, Nov. 4, 191 5. 

1917. — ''Tunnel for Marseilles Canal, Largest in the World." 
Eng. News, Nov. 30, 1916. 

"Construction Methods for Rogers Pass Tunnel." A. C. 
Dennis. Proc. Am. Soc. C. E., Jan., 1917. 
"New Methods in Tunneling in Soft Ground. L. G. 
Warren. Eng. News, Feb. 8, 191 7. 

"The Harlem River Subway Tunnel, New York." F. W. 
Skinner. Engng., July 13, 191 7. 

"Subaqueous Tunneling at its Worst." C. M. Holland. 
Comp. Air Mag., Apr., 1917. 

"Tunnel under Hudson River, New York, Designed for 
Vehicular Traffic." Eng. News-Rec, Apr., 19, 191 7. 

1918. — "The Use of the Air Hammer-drill in Tunneling." 

B. Owen, Commonwealth Engineer, Melbourne, AustraUa. 
July, 1918. 

"Repairing Tunnel Linings with Gunite." Com. Air, Mag. 
June, 1918. 

1919. — "The Mount Royal Tunnel." J. L. Busfield. Jour. 
Eng. Inst, of Canada, Vol. 2, No. 4, Apr., 1919. 
"Concrete Block Tunnel Lining at River Rouge, Mich." 
Bull. Gen. Contr. Assn., Vol. X, No. 8, Aug., 1919. 
"Hudson River Tunnel Problems, Structural and Construc- 
tion." W. C. Parmley. Eng. World, Vol. XV, No. 3, 
Aug. I, 1919. 

"Proposed Vehicular Tunnel under the Hudson River at 
New York." Ry. Rev., Vol. LXIV, No. 25, June 21, 1919. 
"Vehicular Tunnels under the Hudson River at New York." 
M. Schreiber. Jour. Frank. Inst., Vol. CLXXXVII, No. 3, 
Mar., 1919. 

1920. — "The Proposed New York and New Jersey Vehicular 
Tunnel, New York, Hudson River." Trans. Am. Soc, 

C. E., Vol. LXXXm, 1920. 



576 MODERN TUNNELING 

''Notes on Tunnel Lining for Soft Ground." B. H. M. 
Hewett and S. Johannesson. Trans. Am. Soc. C. E., Vol. 
LXXXIII, 1920, 

192 1. —"Tunnel Widening on the Virginian Railway. Enlarge- 
ment of Tunnel Bores Necessitated by Double Tracking 
Involving Special Engineering Features." Ry. Rev., 
Chicago, Vol. LXVIII, No. 11, Mar. 12, 1921. 

BOOKS 

" Tunneling, Explosives Compounds and Rock Drills." Henry 
S. Drinker. Published by John Wiley & Sons, New York, 
3d Edition, 1888, 1143 pp., 20 plates, 1000 cuts. 

" Practical Tunneling." Frederick Walter Simms. With addi- 
tional chapters illustrating recent practice, by D. D. 
Kinnear Clark. Crosby Lockwood & Son, London, 1896; 
548 pp. 

" Tunneling. A Practical Treatise." Charles Prelini. With 
additions by Charles F. Hill. David Van Nostrand Co., 
New York, 1901; 307 pp. 

" Tunnel Shields and the Use of Compressed Air in Subaqueous 
Works." W. C. Copperthwaite. D. Van Nostrand Co., 
New York, 1906; 389 pp. 

'' Subways and Tunnels of New York." G. H. Gilbert, L. I. 
Wightman and W. L. Saunders. John Wiley & Sons, New 
York, 1912, ist Edition; 372 pp. 

" Tunneling. Short and Long Tunnels of Small and Larger 
Section Driven through Hard and Soft Materials." 
Eugene Lauchli. McGraw-Hill Book Co., New York; 
I st Edition, 191 5; 230 pp. 



APPENDIX 

OUTLINE OF TUNNEL DATA 

The following outline is intended to cover the more im- 
portant features to be considered in making a tunnel examina- 
tion: 

General: 

Name of company operating. 

Head office. 

Officials. 

Consulting engineer. 

Field superintendent. 

Names and officials of former companies. 

Superintendent of each. 

Dates of starting, etc. 

Tunnel: 

Size. 

Form. 

Length. 

Elevation of portal. 

Character of rock. 

Grade. 

Size and shape of water drain. 

Style of timbering where necessary. 

Amount of timbering. 

Power Plant: 

Description and arrangement. 

Sizes of machinery. 

Cost of plant. 

Efficiency. 

Cost of power. 

Compressors : 
Make. 
Size. 
Speed. 

577 



578 MODERN TUNNELING 

Rated capacity. 
Actual capacity. 
Efficiency. 
, Repairs. 
Length and size of delivery pipe. 
Arrangements for removing water in air. 

Ventilation: 

Make of fan or blower. 

Size. 

Speed. 

Amount of pressure or vacuum. 

Rated capacity. 

Actual capacity. 

Efficiency. 

Repairs. 

Size of ventilating pipe. 

Thickness of metal. 

Method of jointing. 

Length of sections. 

Where carried in tunnel. 

Distance of end of pipe from face of tunnel. 

Direction of air current. 

Length of time required to clear after each round of shots. 

Drilling: 
Make. 
Size. 

Number of drills in face. 
Cost of repairs. 
Method of mounting. 
Air pressure at drills. 
Air consumption. 

Number, depth, and direction of holes in each round. 
Rate of drilling. 

Brand, size, and form of steel used. 
Durability of same. 
Method of sharpening. 
Number sharpened per day. 
Number of drill shifts per day. 
Number of drillers and helpers. 

Time required in setting up drills, in drilling the round, and in 
taking down drills. 



APPENDIX 579 

Blasting: 

Make of explosives. 

Brand. 

Size of sticks. 

Strength. 

Method of loading. 

Tamping. 

Method of firing. 

Size of wire, make of battery, precautions against short circuits 

if electric firing is used. 
Speed of fuse. 
Method of igniting same. 
Order of firing. 

Method of making primers, and size of detonators. 
Their position in the holes. 

Time required to clean out holes, load, and shoot. 
Temperature of rock at the face. 
Temperature of dynamite when placed in the hole. 
Amount of rock broken per pound of explosive. 
Arrangements for storing explosives. 
Arrangements for thawing explosives. 

Mucking: 

Number of mucking shifts per day. 

Number of muckers. 

Position in which they work. 

Size and form of shovels used. 

Is shoveling done from tunnel floor, planks, or steel plate ? 

Method of handling cars in heading. 

Time of loading each car. 

Time of mucking for each round. 

Tramming: 

Horses, mules, electricity, or compressed air. 

Gauge of tracks. 

Weight of rail. 

Arrangement of switches in tunnel and at face. 

Dimensions of cars. 

Capacity of cars. 

Type of cars. 

Arrangements for facilitating dumping. 

Design, size, and material in wheels. 

Method of oiling. 



580 MODERN TUNNELING 

Method of coupling. 

Brakes. 

Repairs. 

Durability. 

Wages : 

Division of labor for entire work. 
For each individual shift. 
Class of men employed. 
Wages paid each. 
Details of bonus if offered. 

Speed: 

Per shift. 

Twenty-four hours. 

Month. 

Observations on contributing causes. 

Cost: 
Labor: 

Engineering. 

Superintendence. 

Shift foremen. 

Bookkeepers. 

Time-keepers. 

Drillers. 

Helpers. 

Muckers. 

Motormen. 

Mule drivers. 

Dump men. 

Blacksmiths. 

Helpers. 

Machinists. 

Electricians. 

Power engineers. 

Track men. 

Carpenters. 

Tram men. 

Any others, stating nature of duties. 

Materials: 
Powder. 
Fuse. 



APPENDIX 581 



Materials (Continued) : 
Caps. 
Candles. 
Carbide. 
Light globes. 
Timber 
Lumber. 
Ties. 
Track. 

Ventilating pipe. 
Pressure air pipe. 
Water pipe. 
Hose. 

Machine oil. 
Shovels. 
Picks. 

Steel for drills. 
Blacksmiths' supplies. 
Blacksmiths' fuel. 
Machinists' supplies. 
Horse feed. 
Miscellaneous. 

Repairs: 

Power machinery. 

Haulage equipment. 

Compressors. 

Ventilating machinery. 

Other machinery. 

Drills. 

Pipe. 

Track. 

Electric line. 

Telephone. 

Buildings. 

Picks and shovels. 

Miscellaneous. 

Power, not including labor, repairs, or depreciation' 
For drilling. 
Tramming. 
Ventilating. 
Miscellaneous. 



582 MODERN TUNNELING 

Depreciation: 
Power machinery. 
Haulage equipment. 
Compressors. 
Ventilating machinery. 
Other machinery. 
Drills. 
Pipe lines. 
Track. 
Electric line. 
Telephone. 
Buildings. 
Miscellaneous. 

General expenses. 

Miscellaneous expenses, stating nature. 

Illumination: 
Permanent. 
Hand. 

Signaling: 

Electric bell. 
Mine telephone. 
Other methods. 

Special Difficulties: 
Water. 
Bad air. 
Loose ground. 
Poisonous gases. 
Inaccessibility. 
Excessive freight rates. 
Any others, stating nature. 

Conclusions: 

Observations, commendations, and criticisms of methods em- 
ployed. 



INDEX 

PAGE 

Accessibility of tunnel, influence of, on choice of power 66 

Accidents, electrical, causes of 311 

prevention of 313, 321, 324, 326 

from explosives, causes of 293-304 

prevention of 293-304, 319, 322, 325 

from roof falls, causes of 290-292 

prevention of 290-292, 319, 321, 324 

in tunneling, frequency of 289 

haulage, causes of 309 

prevention of 309, 320, 323, 326 

Acetylene, advantages of 204 

cost of 204 

use of, in tunneling 201, 204 

Adit, definition of 2 

Aftercooler, for air compressors, purpose of 106 

Agricola, on mining 11 

Air, compressed, consumed by drills 83 

cooling of 102 

danger from high temperatures in loi, 107 

for transmitting power 64 

losses of 83 

See also Compressed air 

Air compression, dangers of high temperatures produced during lOl 

heat produced during loi 

moisture produced during 105 

Air compressors, aftercooler for, purpose of 106 

air receivers for, purpose of 107 

belt driven, straight-line, two-stage type, figure showing 88 

capacity of, loss of, causes of 83, 84 

rating of 82 

and power required by 82 

cause of explosions in 102 

direct-connected, electrically driven, duplex, two-stage type, fig- 
ure showing 92 

duplex, features of 88 

duplex, compound-steam, two-stage type, figure showing 90 

duplex, simple-steam, two-stage type, figure showing 89 

efficiency of 109 

features of 80 

heat losses in 102 

intercooler for 104 

583 



584 INDEX 

PAGE 

Air compressors, power required by 82 

power requirements of 109 

precoolers for, need of 106 

production of harmful gases in 305 

proper size of, determination of 82, 83 

regulation of, methods used for 97-100 

relative merits of types of 94-97 

selection of, factors determining 80, 94, 109 

single-stage, power-driven type, figure showing 88 

single-stage, tandem type, figure showing 86 

straight line, features of 85-88 

straight-line type, figure showing 87 

turbine type, power required by 82 

types of 80, 85, 94, 96 

unloaders for 99 

volumetric efficiency of 83 

Air consumed by man at work 116 

Air drills, advantages of 147, 148 

air thrown valve type, merits of 155 

auxiliary valve type, merits of 156 

bar mounting for 212 

column mounting for ; ; 212 

cost of repairs for 153, 154 

features of 130 

hammer type, merits of 160 

piston type, figure showing 132, 133, 134, 137 

merits of 149 

selection of, factors influencing 160, 161 

tappet valve type, merits of 155 

types of 130 

valveless, features of 136 

figure showing 137 

merits of 1 56 

valves for 131-136 

ventilation supplied by 148 

Air, for ventilation, quantity needed 115-1 18 

pressure of 1 19-12 1 

Air locks 562 

Air meters, types of 127, 128 

Air pipe lines, drains for, need of 108 

leakage in, methods of determining 84 

precautions in construction of 84 

Air receiver, functions of 107, 108 

Air required, by man for breathing, table showing 116 

for ventilation of tunnels 1 15, 1 16 

Air-thrown valve rock drill, features of 132 

merits of 155 



INDEX 585 

PAGE 

Air transmission, size of pipe required for 121, 122 

Alinement ; 432 

Ammonia dynamite, See Dynamite 

Animals, accidents from, causes of 311 

amount of air required by 115 

for tunnel haulage, merits of 173 

Anne of Lusignan, early tunnel started by 1 1 

Arch sets, arrangement of timber in 277, 278 

Arlberg tunnel (Austria), cost of 25 

features of 26 

progress of 26 

Arthur's Pass tunnel (New Zealand), mention of 31 

Aspen tunnel (Wyoming), mention of 31 

Assassin tunnel (France), cost of 18 

Auburn tunnel (Penn.), mention of 13 

Austria, early railway tunnels in 14 

Automobiles, clearance for 430 

exhaust gases 457 

Auxiliary valve rock drill, features of 135, 136 

merits of 1 56 

Aztecs, tunneling by 7 

B 

Bar mounting for drills 212 

Beams, needle 517 

Beaumont-English rotary tunneling machine 508 

Bench drilling 494-495 

Bench and heading, kept close together 496 

Bennett tunneling machine, features of ' 185 

Bethell process for preserving timber 272 

Bibliography 361-419 

air drills 394 

air compressors 395 

blasting methods 406 

blasting supplies 408 

Chapters XVIII-XXII • 568-576 

choice of power 382 

compressed-air accessories 391 

compressed-air power 380 

compression of air 388 

costs 418 

drilling accessories 397 

drilling methods 405 

electric drills 396 

electric power 378 

gasoline drills 397 

haulage 398 



586 INDEX 



PAGE 



Bibliography, hydraulic drills 395 

illumination 402 

internal-combustion power 373 

methods of tunnel driving 402 

mucking 411 

power-plant descriptions 382 

power transmission 381 

safety and health . . * 414 

speed records 412 

steam power 371 

timbering 411 

tunnel descriptions 360 

tunneling machines , 401 

ventilation 393 

water-power 369 

Bids, contract : 458-460 

Big Bend tunnel (Calif.), features of 23 

Big Creek tunnel (Calif.), mention of 23 

Black Rock tunnel (Pa.), mention of 15 

Blast-holes, arrangement of 221 

chambering of 227 

charging of 240, 249-251 

depth of 229-235 

at various tunnels, table showing 235 

method of firing 122 

number of 219 

placing of 221-229 

position of primer in 249-251 

Blasting cap. See Detonator 

Blasting powder, black, gaseous products of 238 

Blasts, effectiveness of, factors affecting 227 

Blisworth tunnel (England), mention of 13 

Blowers, comparison with fans for ventilation 122 

pressure, figure showing 1 1 1 

relative merits of 1 1 1 , 122 

Boilers 558 

Bonticou tunnel, Catskill Aqueduct, features of 37 

Bottom cut, arrangement of holes in 224, 228 

description of 224 

figure showing 225 

Brick work (lining) 436, 531-532 

Brunton & Trier rotary tunneling machine 508 

Buffalo Water tunnel (N. Y.) blast holes in, arrangement of 222 

depth of 235 

cars used in 1 69 

features of 49 

quantity of explosives used in 243 



INDEX 587 



PAGE 



Buffalo Water Tunnel (N. V.), wedge cut at, figure showing 223 

Buildings, surface, fire in, danger of 313 

Bureau of Mines, officials of, acknowledgments to 3 

Burleigh drills, use of, in Hoosac tunnel 25 

Burleigh tunnel (Colo.) 35 

features of blast holes in 219 

Burnettizing timber, method of 272 

Busk-Ivanhoe tunnel (Colo.), details of 30 

C 

Caisson method 554-557 

Call bell, for underground telephones 207 

Camp 479-48 1 

Canal tunnels, American 13 

English 13 

French 12 

Candles, dangers in use of 203, 315 

for illumination, merits of 203 

Cap, blasting. See Detonator 

Capacity of ventilating pipe, table showing 120 

Carbon dioxide, flows of, in Los Angeles Aqueduct 305 

from gasoline locomotives, method of handling 178 

in rocks, dangers from encountering 305 

properties of 303 

Carriage mounting for drills, merits of , 214, 217 

Cars, size of 471-473, 475 

tunnel, derailments of, delays from 292 

desirable features of 163, 265 

handling of, method of 262-265 

size of 163 

Carter tunnel (Colo.), air pressures used at 103 

blast holes used in heading of 219 

blast holes in, depth of 235 

bottom cut in, figure showing 225 

cars used at, features of 169 

consumption of air by drills in 83 

cost of drill repairs at 154 

direction of air current in 1 14 

drilling speed at 151 

features of 35 

grade of dynamite used at 241 

power plant at, water supply for 66 

pressure required for ventilating current 120 

system of lighting in 202 

Catskill Aqueduct tunnels (N. Y.), cars used at, features of 169 

depth of blast holes in 235 

features of 36 



588 INDEX 



PAGE 



Catskill Aqueduct tunnels (N. Y.), grade of dynamite used in 241 

quantity of explosives used 243 

siphons of, linings of 287 

speed of drilling in 151 

system of lighting in 202 

Caved ground, timbering for 280 

Caves, water-filled, danger from 316 

Cement gun 532-533 

Central power stations, economy of 66 

Central tunnel (Colo.), air pressures used at 103 

cars used at, features of 169 

depth of blast holes in 235 

direction of air current in 114 

drilling speed at 151 

features of 39 

grade of dynamite used in 241 

pressure required for ventilation current at 120 

system of lighting at 202 

Chambering of blast holes, comment on 227 

Chipeta adit (Colo.), blast holes in face of '. . . . 219 

cars used at, features of 169 

features of 49 

Choice of power for tunnel work, factors governing 65 

Clearance, automobiles 430 

standard 429 

Cofiferdam methods ' 557-558 

Column mounting for drills, methods of 213-216 

Comparison of fans and blowers for ventilation 122 

Compressed air, hours of work in 561 

meters for, value of 127 

pipe lines, drains for 108 

leakage in, method of testing for 84 

plant 559-561 . 

power transmission by 64 

removal of moisture from 105 

thermal losses in loi 

transmission of, cost of 70» 73 

use of, for ventilation 148, 305 

working pressure of 103 

See also, Air, compressed 

Compressed air locomotives, use of 173 

Compressors, air, reliablity of prime importance 468 

Compressors, See Air compressors 

Concrete, mass (lining) 436 

precast (lining) 437 

pneumatic placement 527~53i 

Conemaugh tunnel (Pa.), mention of < . . , 14 



INDEX 580 



I'AC.li 



Construction 461-481 

Consumption of fuel, influence of, on choice of power 74 

Contract bids 458-460 

Coquitlam tunnel (B. C), mention of 23 

Corbett tunnel (Wyo.), features of 22 

Cornelius Gap tunnel (Ore.), car used at 169 

features of 49 

Coronado tunnel (Ariz.), cost of driving 329 

features of 39 

Cost, excavation in hard rock 486-490 

shield driven iron-lined tunnels 564-566 

soft ground 542-543 

trench type 566-567 

Cost of railway tunnels 25 

Cost of tunneling 328-359 

See also various tunnels named 

Cowenhoven tunnel (Colo.), caves in 317 

timbering in, method of 282 

Creosote, use of, for preserving timber 271, 272 

Crimping tool, for explosives, use of 301 

Cross-section, factors controlling 429 

independent of span 544 

Current, electric, purchased, as source of power 76 

D 

Delia S. mine (Colo.) cave in, flow of water from 317 

Depreciation, charges for 77 

Depth of drill holes 229 

at various tunnels, table showing 235 

Design of tunnels 426-460 

Detonator, amount of explosives contained in, table showing 248 

definition of 247 

delay-action, features of 255 

electric, figure showing 247 

grades of, rating of 248 

ignition of 247 

position of, in primer 310 

proper use of 300 

strength of 301 

Diesel engine, advantages of 63 

as a source of power 53 

characteristics of 62 

Direction of holes in tunnel headings 221 

Direction of ventilating current, factors influencing 1 13 

Double versus single tunnels 429 

Drainage and pumping 451-455, 476 

Drains for compressed air pipe lines, need of 108 



590 INDEX 



PAGE 

Drift, definition of 3 

Drill, See Air drill. Rock drill 

Drill holes, depth of, at various tunnels, table showing 235 

determination of 229 

shallow, merits of 231 

See also Blast holes 

Drill mounting, bar 490 

column 490 

travelling carriage 491 

Drill mountings, adaptability of various types 217 

amount of mucking required with various types 215 

choice of 218 

horizontal bar, method of using 213 

vertical column, merits of 214 

Drill sharpening machines, advantages of 125 

capacity of 126 

types of 125 

Drill shifts per day, single, merits of 209 

three, merits of 211 

two, merits of 210 

Drilling operations, cycle of in Simplon tunnel 28 

Drilling, single shift system of 209 

speed at various tunnels, table showing 151 

test, advanced 509 

three-shift system of 211 

two-shift system of 210 

typical methods 493 

Drilling machines. See Air drills. Rock drills 

Drills 468 

racks for, advantages in using 207 

Drinker, H. S., on early history of explosives and rock drills 19 

on early railway tunnels 14 

Drivers, precautions to be taken by 310 

Drunkenness, See Intoxication 

Dump, cradle, description of 180 

for cars, types of 178 

Dumping, derrick for, use of 179 

Dumping device, cradle, use of 179 

revolving, use of 1 79 

types of 178-180 

Dynamite, ammonia, composition of 237 

gaseous products of 238 

amount of, used at various tunnels 243 

burning of, noxious gases from 303, 304 

prevention of 303 

charging of 295, 297 

detonation of 250 



INDEX 591 

PAGE 

Dynamite, for tunneling, selection of 240 

gases from 237, 249 

gelatin, advantages of 239 

composition of 236 

gaseous products of 238, 303 

rating of strength of 239 

strength of detonators for 301 

handling of, precautions in 293, 296, 322 

misfires of 299 

premature explosions of 296 

proper method of storing of 257 

proper method of thawing of 258 

proper strength of detonators for 301 

storing of 257 

precautions in 294 

thawing of, need of 253 

precautions in 294 

use of, care in 324 

E 

Earth pressures 435 

Economics 424 

Efficiency, maximum obtainable from blast hole 226 

thermal, influence of on choice of power 75 

volumetric, of air compressors 83 

Egyptians, stone-cutting tools of 5 

tunnels driven by 5 

Electricity, accidents from, causes of 311 

prevention of 321, 323, 326 

cost of 76 

purchased, as source of power 76 

transmission of, best voltages for 71 

cost of 70, 7 1 

method of 71 

Electric detonator, figure showing 247 

Electric drill, durability of 159 

merits of 157-159 

types of 141-147, 157 

Electric lamp, advantages of 203 

Electric locomotives, shocks from, precautions against 313 

use of 174 

Electric motors, types of 64 

Electric plant 562-563 

Electric power, advantages of 64 

Electric voltages, best for transmission lines, determination of 71 

Elizabeth Lake tunnel (Calif.), consumption of air by drills in 83 

cost of driving 342 



592 INDEX 

PAGE 

Elizabeth Lake tunnel (Calif.), features of 43 

quantities of explosives used in 243 

timbering in 284 

timbering in, figure showing 285 

Elizabethtown tunnel (Pa.), mention of 15 

Engines, internal combustion 457 

England, early railway tunnels in 14 

English Channel, tunnel under, use of tunneling machines in 183 

Equipment, haulage 470-475 

loading ; 468-470 

shield 550-553 

surface 478-479 

Ernst August StoUen (Germany), details of 16 

Excavating machinery 508-553 

Excavation, cost of . 486-490 

disposal of 496 

estimates for 489 

in hard rock, methods of 482-509 

in soft ground, methods of 510-543 

Exhaust gases, automobiles 457 

Exits, separate, need of 314 

Explosive, accidents from use of 293 

precautions against 293-303 

charge of, determination of 241 

choice of detonators for 249 

chronology of 19 

excessive charges of, dangers from 290 

firing of, precautions in 295 

gaseous products from 238, 303 

handling of, precautions in 293, 296, 322 

high, burning of, cause of 303 

high, proper strength of detonator for 301 

methods of loading 249 

misfires of, causes of • • • • 299 

proper method of thawing of 258 

proper method of storing of 257 

premature explosions of 296 

rating of strength of 239 

risks in loading 297 

selection of, factors determining 236, 239 

sensitiveness of 297 

slitting of cartridges of 253 

storing of, precautions in 294, 257 

thawing of, methods 258 

thawing of, necessity for 253 

thawing of, precautions in 294 

use of, precautions in 293-295, 322, 324 



INDEX 593 

I'AGli 

Explosive, use of two grades of, at headings 240 

work of, factors affecting 226 

F 

Falls of roof, causes of 290 

False set, see Timbering 

Fans, comparison with blowers for ventilation 122 

Fans, ventilating, use of 1 1 1 , 122 

Fatalities in tunneling, rate of 289 

Fernald, R. H., on cost of producer-gas plants 69 

Ferroux drills, results with, at Arlberg tunnel 27 

Fires in tunnels, causes of 314 

dangers from 314 

danger from, avoidance of 314, 321, 324, 327 

Fire setting, method of excavation 9 

Firing blasts, methods of 254 

First tunnel in United States 420 

Foreign systems timbering 461, 510 

Foreman, suggestions for 321 

Forms, collapsible 525-527 

concrete 52 1-525 

Forepoling, definition of 280 

Fort Williams tunnel (Ontario), blast holes in face of 219 

depth of blast holes in 235 

drilling speed at 151 

features of cars used at 169 

system of lighting at 202 

Fowler, tunneling machine, features of 185 

France, early railway tunnels in 12, 14 

Free Silver mine (Colo.), rushes of water in 317 

Freiberg district (Germany), early use of pow'der in 12 

Fuel consumption, influence of, on choice of power 74 

Fuse, miner's, danger of lacing through cartridge 253 

gases from burning of 257 

handling of, precautions in 298, 299 

method of lighting 254 

rate of burning of 244-246 

causes of variations in 246 

selection of, importance of 300 

storage of, precautions in 247, 299 

Fuse igniter, description of 256 

G 

Gas engines, producer, as sources of power 59 

Gas, from explosives, danger of 303 

harmful, precautions against 325 



594 INDEX 

PAGE 

Gas, inflammable, at heading, method of burning 306 

method of removing 309 

See also Carbon dioxide. Carbon monoxide 

Gases, exhaust (automobiles) 457 

Gas power, producer, selection of, conditions governing 76 

Gas producer, as a source of power 53 

description of principles of 60, 61 

Gasoline engine, advantages of 53, 59 

as sources of power 59 

Gasoline locomotives, advantages of 176 

cost of haulage by 177 

for haulage, cost of, table showing 177 

use of 59, 176, 177 

Gelatin dynamite, See Dynamite 

Geology, study of essential in design 426 

Germany, early railway tunnels in 14 

Gold Links tunnel (Colo.), air pressures used at 103 

blast holes in 219 

depth of 235 

cars used at, features of 169 

direction of air current in 114 

drilling speed at 151 

features of 39 

grade of dynamite used in 241 

system of lighting used in 202 

Grand Central sewer (N, Y.), blast holes used in face of 219 

cars used in 169 

features of 50 

Grant's Hill tunnel (Pa.), mention of 14 

Greeks, early tunnels driven by 6 

Ground, heavy, defined 421 

light, defined 42 1 

prevention of movement 519-520 

running 514 

soft defined 42 1 

treacherous defined 422 

Gunnison tunnel (Colo.), air pressures used at 103 

blast holes, in face of 219 

depth of 169 

cars used at, features of 169 

cost of drill repairs at 153 

cost of driving 331 

depth of blast holes in 235 

direction of air currents in 114 

features of 39 

grade of dynamite used in 241 

quantity of dynamite used in 243 



INDEX 595 



Gunnison tunnel (Colo.), system of lighting 202 

Gunpowder, early use in tunneling 11 

"Guns," in blasting, definition of . 299 

H 

Hacklebernie tunnel (Pa.), mention of 18 

Handling cars in tunnels 263 

Hard rock, bench drilling 494-495 

disposal t 496 

drill mounting, bar 490 

column 490 

travelling carriage 491 

excavation, cost of 486-490 

estimates for 489 

excavation methods in 482-409 

heading and bench kept close together 496 

heading center 499-505 

heading, size of 484-486 

heading top or bottom 497-499 

overbreakage 505 

packing 508 

rotary cutters T . . . 508 

test drilling, advanced 509 

typical drilling methods 493 

Harecastle tunnel (England), mention of 13 

Harz mines (Germany), early use of gunpowder in 12 

Haulage, by gasoline locomotive, cost of, table showing cars for 163-169 

data concerning, table giving 169 

figure showing 164, 165, 166, 167, 168 

cars, size of 471-473, 475 

equipment 470-475 

tipple 475 

track, gage 471-472 

maintenance of 473 

motive power for, choice of 173-178 

use of animals for 1 73 

use of compressed-air locomotive for 173 

use of electric motors for 173 

Haulage accidents, causes of 309 

precautions against 320, 323, 326 

Hay, storage of, in tunnel, danger of 315 

Heading, advantages of three shifts at 211 

and bench kept close together 496 

bottom 515 

center 499-505 

location 514 

pioneer 499-505 



596 INDEX 



Heading, railway tunnel, comparison with mining tunnel 24 

size of 484-486 

timbering for 283 

top or bottom 497-499 

wall plate 5i3, 5i6 

Heat produced during air compression loi 

removal of 102 

Heaters for thawing houses 259 

Herrick, R.'L., on Los Angeles Aqueduct 284 

Hicks, G. S., Jr., air transmission, formula of 119 

Hindus, caves excavated by 6 

Hole, See Blast hole 

Holes, direction of, in tunnel headings 221 

number of, in tunnel headings 219 

Hoosac tunnel (Mass.), details of . 25 

progress and cost of 25 

tunneling machines tried at 181 

use of air drills at 25 

Horizontal bar mounting for drills, method of using 213 

Hose, supports for, advantages of 207 

Hummingbird tunnel (Idaho), mucking machine at, figure showing 170 

Hydraulic compressor, as source of power 55 

Taylor, details of 56 

figure showing . , 56 

use of, at Mt. Cenis tunnel 55 

Hydraulic drills, features of 138-141 

merits of 1 56 

Hydraulic power plant 563 

Hydrocarbon gas, from rocks, burning of 306 

in tunnels, dangers from 306 

explosibility of 306 

I 

Illumination, means of, at various tunnels, table showing. 202 

Illumination of tunnels, See Lighting 

Impulse wheels, water, regulation of 98 

India, early excavations in 6 

Installation cost, influence of, on choice of power 66 

Insulation of electric conductors, need of close inspection of 312 

Intercooler, construction of 104 

figure showing 104 

need of 104 

Interest on capital invested, charge for 77 

Internal-combustion engines, as sources of power 59 

efficiency of small sizes of 76, 76 

Internal combustion engines, exhaust gases 457 



INDEX 597 

PAGE 

Intoxication, as cause of accidents 318 

Iron, cast (lining) 439-444 



Japanese tunnels, list of 33 

Joker tunnel (Colo.), blast holes in, arrangement of 219 

depth of 235 

drilling speed at 151 

features of 50 

system of lighting 202 

Joseph II Stollen, mention of 16 

K 

Karns tunneling machine, features of 186 

Kellogg tunnel (Idaho), features of 50 

Kelty tunnel (Scotland) , features of 21 



Labor required, influence of, on choice of power 74 

Lagging, definition of 280 

Lake Albanus (Italy), early drainage tunnel for 8 

Lake Coxamarco (Peru), early drainage tunnel for 7 

Lake Fucinus (Italy), early drainage tunnel for 8 

Lamps, acetylene, merits of 204 

electric, merits of 203 

oil, open flame, use of 202 

Laramie Poudre tunnel (Colo.), l)last holes in, arrangement of 219 

depth of 235 

order of 224 

cars used in, features of 169 

figure showing 166, 176 

consumption of air by drills 83 

cost of driving 332 

direction of air current in 114 

drilling speed at 151 

exhauster used at 118 

features of 40 

grade of dynamite used in 241 

lengths of shifts at 74 

mounting of drills at 213 

mucking, manner of 262 

power plant, at water-supply for 66 

pressure required for ventilation 120 

quantity of explosives used in 243 

speed of driving 233 

system of lighting 202 



598 INDEX 

PAGE 

Larium (Greece) tunnels, In silver mines of 7 

Lausanne tunnel (Pa.), blast holes in, arrangement of 219 

depth of 235 

cars used at, features of 169 

direction of air current in 114 

dump used at 1 80 

features of 40 

grade of dynamite used in 241 

system of lighting in 202 

Leakage in compressed air pipe line, method of testing for 84 

Lebanon tunnel (Pa.), mention of 13 

Liberty tunnels, Pittsburg, Pa 533-542 

Life of power plant, influence of, on choice of power 65 

Lighting 457, 477, 478 

Lighting of tunnels, method of 201 

Lining, backing of 447 

brick work 436 

cast iron 439-444 

cast steel 439 

concrete, mass 436 

concrete, precast 437 

defined 422 

earth pressures to be resisted 435 

materials used 439 

methods . 520-542 

stone masonry 436 

structural steel 444-447 

timber 433 

waterproofing, various methods 448-451 

when required 432 

wood 553 

List of Japanese tunnels 33 

of noted railway tunnels, table giving 32 

of patents for tunneling machines 188-201 

Loading blast-holes, precautions in 295 

Loading equipment 468 . 470 

Loading machines, figure showing 170, 172 

types of 170-173 

Loetschberg tunnel (Switzerland), carriage mounting for drills 214 

details of 29 

drills employed at '. . 29 

number of muckers employed in 261 

progress and cost of 25 

quantity of explosives used 243 

speed of mucking in 216, 263 

Loose Rock, See soft ground 

Los Angeles Aqueduct (Calif.), air pressure used in 103 



INDEX 599 

PAGE 

Los Angeles Aqueduct (Calif.), blast holes in 219 

carbon dioxide encountered in 305 

cars used at 169 

figure showing 167 

cost of drill repairs at 154 

cost of driving tunnels of 333-342 

cost of electric power for 76 

direction of air current in 114 

drilling speed in 152 

features of 41 

grade of dynamite used in 241 

lining of, thickness of 287 

officials of, acknowledgment to 3 

pressure of ventilation current 120 

system of lighting 202 

use of equipment in 66 

Lucania tunnel (Colo.), air pressure used at 103 

cars used at, features of 169 

consumption of air by drills in 83 

cost of drill repairs at 154 

cost of driving 343 

depth of blast holes in 235 

direction of air current in 114 

drilling speed in 151 

features of 43 

grade of dynamite used in 241 

pressure of ventilation current 120 

system of lighting 202 

M 

Machinery for ventilation, selection of, factors determining 123 

Malpas tunnel (France), mention of 12 

Manager, suggestions to 319 

Marshall-Russell tunnel (Colo.), air pressure used at 103 

blast holes in, arrangement of 219 

depth of 235 

cars used in, features of 169 

consumption of air by drills 83 

cost of drill repairs at 154 

cost of driving 344 

direction of air current in 1 14 

drilling speed at 151 

features of 44 

grade of dynamite used in 241 

pressure of ventilation current 120 

system of lighting 202 



600 INDEX 

PAGE 

Masonry, brick and stone (lining) 436, 531-53 

Mauch Chunk tunnel (Pa.), air pressure used at 102 

Means of lighting at various tunnels, table showing 202 

Metres for compressed air, usefulness of 121 

Mine tunnels, features of 2 

Miner, suggestions to 324 

Misfires, causes of 299 

precautions following 302, 325 

Mission tunnel (Calif.), air pressure used at 103 

blast holes in, depth of 235 

cars used at, features of 169 

consumption of air by drills in 83 

cost of driving 345 

direction of air current in 114 

features of 44 

grade of dynamite used in 241 

pressure required for ventilation 120 

speed of drilling 151 

system of lighting 202 

Moisture produced during air compression 105 

Moodna Siphon, Catskill Aqueduct (N. Y.), features of 37 

Motive power for tunnel haulage, choice of 173-178 

Mount Cenis tunnel (France), progress and cost of 25 

use of air drill at 25 

use of hydraulic compressor at 55 

Mount Royal tunnel (Canada), details of 51 

Mountings for drills, adaptability of various types 217 

amount of mucking required with 215 

choice of 218 

horizontal bar, method of using 213 

vertical column, merits of 214 

Muck, danger from explosives in 302 

picking of, proper method of 302 

Mucking, conditions afifecting speed of 260 

importance of system in 262 

number of men for 261 

positions of men for ., 261 

speed attainable in 216, 263 

use of steel plates in 267 

Mucking machine, figure showing 170 



M 

Naples, Italy, Roman tunnel near 8 

Needle beams 517 

New York Board of Water Supply, acknowledgments to 3 

Newhouse tunnel (Colo.), air pressure used at 103 



INDEX 601 

PAt.K 

Newhouse tunnel (Colo.), blast holes in, depth of 235 

order of 219 

cars used at, features of 169 

direction of air current in 114 

drilling speed at 151 

dumping of cars at 179 

features of 44 

grade of dynamite used in 241 

system of lighting 202 

Nisqually tunnel (Wash.), air pressure used at 103 

blast holes in, depth of 235 

order of 219 

cars used at, features of 169 

direction of air current in 114 

drilling speed at 151 

grade of dynamite used in 241 

power plant of, water-supply for 67 

pressure of ventilating current 120 

system of lighting 202 

Nitrogen peroxide, deadliness of 304 

Nitroglycerine, invention of 19 

use of, in tunnels 19, 25 

Nitroglycerine dynamite, gaseous products of 238 

rating of strength of 239 

Northwest tunnel (111.) blast holes in, depth of 23 

order of 220 

features of 51 

Noted railway tunnels, table giving list of 32 

Notre Dame tunnel (France), cost of 18 

Number of holes in tunnel headings, table showing 219 

O 

Oil engines, as sources of power 53 

Ontario tunnel (Utah), features of 45 

Ophelia tunnel (Colo.), blast holes in, depth of 235 

order of 220 

drilling speed at 151 

features of 51 

system of lighting 202 

Outside line of tunnel not to be broken 431 

Overbreakage 505 

P 

Packing back of lining 505 

Packing in hard rock 508 

Patents for tunneling machines, list of 188-201 

Pawpaw tunnel (Md.), mention of . 14 



(302 INDEX 



PAGE 

Pelton wheel, figure showing 54 

proper speed for 55 

Peruvians, ancient mines and tunnels of 7 

Pilot tube method 520 

Pioneer heading 495-505 

Pipe for ventilation, size of 121 

Pipe lines, compressed air, leakage in, method of testing for 84 

Plant 465-481, 558-564 

Pneumatic placement of concrete 527 

Positions of men for mucking 261 

Powder headache, cause of 303 

Powder smoke, removal of, air required for 117 

Power, for tunneling, sources of 53 

gas producer, selection of, conditions governing 76 

most suitable, selection of 64, 65 

sources of : 466-467 

plant, cost of machinery for 66 

depreciation of, charge for 77 

fuel consumption of 74 

labor requirements of 74 

life of, influence of, on choice of power 65 

most economical equipment for 65 

producer gas for 69 

steam, efficiency of 75 

types of 53, 78-80 

Power transmission, cost of 64, 70 

electricity for 79 

means of 64 

Precast block lining 437, 531 

Precoolers for air compressors, need of 106 

Pressure of ventilating current . 1 18-120 

formula for determining 119 

^, table showing 119 

Pressure, loss of, in ventilating pipe 119 

Pressures, earth 435 

Primers, handling of 297 

preparation of 301 

proper place of, in charge 249 

Producer gas, advantages of 64 

transmission of, cost of pipe for 73 

possible distance of 64 

Producer-gas engines, as sources of power 59 

use of in Thames River tunnel (England) 60 

Producer-gas plant, selection of, conditions determining 79 

thermal efficiency of 76 

Producer-gas power, selection of, conditions governing 76 

Progress of railway tunnels, table showing 25 



INDEX ()0;i 

I'AtJE 

Pumping and drainage 451-455, 476 

Purchased current, as source of power 76 

Pyramid cut, figure showing 224 

most effective arrangement of holes in 228 

R 

Ragged Chutes (Ontario), hydrauHc compressor at 56 

Railroad tunnels, definition 420 

Railway tunnels, cost of 25 

details of 32 

early 14 

noted, table giving list of 32 

progress and cost of, table showing 25 

Rand mine (So. Africa), large turbo-compressors at 94 

Rawley tunnel (Colo.), air pressure used at 103 

blast holes in, depth of 235 

order of 220 

cars used at, features of 169 

consumption of air by drills in 83 

cost of driving 347 

drilling speed at 151 

features of 45 

grade of dynamite used in 241 

handling of cars at 265 

speed of mucking at 253 

system of lighting at 202 

ventilation current at 114, 118, 120 

blast holes in, depth of 235 

Raymond tunnel (Colo.), air pressures used at 103 

order of 220 

car used at, features of 169 

direction of air current in 114 

drilling speed at 151 

grade of dynamite used in 241 

system of lighting 202 

Reasons for tunneling 425 

Regulation of air compressors 97-100 

of water wheels 98 

Removal of heat produced during air compression 102 

Retallack and Redfield tunneling machine, features of 186 

Rix, E. A., on compressed-air calculations 81, 149 

Rock-cutting tools, ancient 5 

Rock drills, air, air consumption of 149 

auxiliary valve for, merits of 156 

merits of 147 

piston type 149, 153 

figure showing 132, 133, 135 



604 INDEX 

PAGE 

Rock drills, air, valves for, merits of _ , 132-136 

figures showing 131-136 

valveless, features of 137 

figure showing 137 

carriage mounting for 214 

choice of, factors determining 160 

comparison of different types 147-160 

early use of 18 

electric, advantages of 157 

durability of 1 59 

features of 141 

figure showing 143, 145, 146 

power consumption of 159 

electric, types of 158, 159 

piston, advantages of 158 

gasoline, disadvantages of 147 

hammer type, advantages of 150 

hydraulic, features of. 138, 157 

figure showing 138 

types of 138, 157 

mounting of 212 

selection of, factors influencing 160, 161 

types of 130 

comparison of 160 

use of, in mine tunnels. See tunnels nam.ed in railway 

tunnels 25, 27, 28, 29 

Rogers Pass tunnel 499~505 

Roger's Pass tunnel (B. C), features cf 51 

Romans, rock-cutting tools of 8 

tunnels driven by 8 

Rondout Siphon tunnel (N. Y.), air pressure used at 103 

blast holes in, depth of 235 

order of 220 

cars used at, features of 169 

direction of air current 114 

drilling speed at 151 

features of 36 

grade of dynamite used in 241 

power plant at, labor requirements of 74 

quantity of explosives used in 243 

use of central power station at 66 

Roof, inspection of, need of care in 321 

sound of, significance of 291 

testing of, importance of 291 

methods for 291, 324 

Roosevelt tunnel (Colo.), air pressure used at 103 

blast holes in, depth of 235 



INDEX 605 

I'AGli 

Roosevelt tunnel (Colo.), blast holes in, order of 220 

car used at, features of 169 

cost of driving 348 

direction of air current in 114 

features of 46 

grade of dynamite used in 241 

pressure of ventilating current at 120 

system of lighting 202 

Rotary tunneling machines 508 

Rotschonberger Stollen (Germany), details of 16 

S 

Saint Gothard tunnel (Switzerland), details of 26 

progress and cost of 25 

Samos (Greece), long mine tunnel at 7 

Sapperton tunnel (England), mention of 13 

Second Raton Hill tunnel (N. M.), features of 52 

Selection of ventilating machinery, factors determining 123 

Severn tunnel (England), details of 30 

Sharpening machines, drill, types of 125 

Shear zones, 'timbering for 280 

Shepard's Pass tunnel (Calif.), features of 47 

Shield for mine tunnels, use of 284 

Shield, complete defined 431 

driven iron lined tunnels, cost of 564-566 

may be best method 517 

roof 553-554 

tunneling 545^554 

Shock, electrical, danger from 311 

Shoshone tunnel (Colo.), cost of 22 

features of 21 

Shovelers, space required by 260 

use of steel plates for 267 

Shovels, loading by power 469 

Sigafoos tunneling machine, features of 187 

Simplon tunnel (Switzerland), details of 28 

flow of water in 28 

hydraulic drill used at, features of 138 

figure showing 138 

progress and cost of 25 

quantity of explosives used in 243 

rock drill used at, features of 157 

Single drill shift per day, merits of 209 

Single versus double tunnels 429 

Siwatch tunnel (Colo.), air pressure used at 103 

blast holes in, arrangement of 220 

depth of 235 



606 -NDEX 

PAGE 

Siwatch tunnel (Colo.), car used at, features of 169 

direction of air current in 114 

drilling speed at 151 

features of 47 

grade of dynamite used in 241 

pressure of ventilating current at 120 

system of lighting 202 

Size of tunnel cars 163 

Size of ventilating pipe, formula for determining 121 

table showing 122 

Snake Creek tunnel (Utah), air pressure used at 103 

blast holes in, depth of 235 

order of 220 

car used at, features of 169 

concrete lining of, figure showing 288 

consumption of air by drills in 83 

direction of air current in 114 

drilling speed at 151 

features of 47 

grade of dynamite used in 241 

pressure of ventilating current • 120 

system of lighting 202 

Soft ground, American system 510-51 1 

bottom heading 515 

brick lining 531-532 

cement gun 532-533 

collapsible forms 525-527 

concrete forms 521-525 

excavation methods in 510-543 

heading location 514 

Liberty tunnels 533-542 

cost of 542-543 

lining methods 520-542 

sequence of 521 

main principle of tunneling in 422 

movement of ground, prevention essential 519-520 

needle beams 517 

pilot tube method 520 

pneumatic placement of concrete 527-531 

precast block lining 531 

running ground 514 

shield may be best method 517 

simplest instance 51 1-5 12 

steel sets, advantages of 518 

timbering, importance of careful work 516-517 

wall plate headings 513, 516 

Sommeiller, hydraulic compressor designed by 55 



INDEX 607 

PAGE 

Spain, ancient tunnels and mines in 9 

ventilation of ancient tunnels in 10 

Spiling, definition of 280 

Spiral tunnels (B. C), blast holes in, depth of 235 

order of 220 

features of 52 

Spitter, definition of 254 

Steam engine, thermal efficiency of 75 

types of 58 

Steam power, selection of, conditions governing 76 

Steam turbine, advantages of 58 

efficiency of 58 

features of 58 

Steel plates, use of, in loading cars 264, 267 

Steel sets, advantages of 518 

Steel, cast (lining) 439 

structural, lining 447 

Stilwell tunnel (Colo.), air pressure used at 103 

blast holes in, arrangement of 220 

depth of 235 

car used at, features of 169 

cost of driving 352 

direction of air current in 1 14 

drilling speed at 151 

features of . . . 47 

grade of dynamite used in 241 

system of lighting in 202 

Stoping drills, features of 137 

figure showing 137 

Stone masonry lining 436 

Storage battery locomotive, use of 174 

Storing of explosives, proper method of 257 

Strawberry tunnel (Utah), air pressure used at 103 

blast holes in, arrangement of 220 

depth of 235 

car used at, features of 169 

consumption of air by drills in 83 

cost of drill repairs at 154 

cost of driving 353-359 

direction of air current in 114 

drilling speed at 151 

dumping of cars at 178 

features of 48 

grade of dynamite used in 241 

pressure of ventilating current at 120 

system of lighting 202 

Subaqueous 544-567 



608 INDEX 

PAGE 

Subaqueous, caisson method : 554-557 

chief trunk line railway tunnels 544 

cofferdam methods 557-558 

compressed air — hours of work in 561 

cross-section independent of span 544 

plant 558-564 

air locks 562 

boilers 558 

compressed air 559-56i 

electric 562-563 

hydraulic power 563 

miscellaneous plant 564 

shields, tunneling 545-554 

air pressure regulation 549 

bracing face while shoving 553 

compressed air first used 545 

description of 547-548 

doors 550 

equipment 550-553 

erector 552 

excavating machinery 553 

grouting 550 

hydraulic pressure 552 

inventor of 545 

mud, work in 549 

rams 551 

rock, work in 550 

roof 553-554 

thrust bars for concrete lining 552 

wood lining 553 

trench type, cost of 566-567 

Superintendent, suggestions to 319 

,Sutro tunnel (Nev.), features of 19 

Swelling ground, timbering for 279 

T 

Tailblock system, timbering for 281 

Taillades tunnel (France), mention of 18 

Talbot tunneling machine, mention of 181 

Tamping, early use of, in tunneling 11 

in tunnel work, merits of 252 

proper amount of 252 

proper method of .• ^ 297 

reasons for using 252 

Tamping bar, proper use of 297 

Tappet valve rock drill, features of 132 

merits of 1 55 



INDEX ()09 

PAGE 

Telephone, installation of " . . 205 

type of, selection of 206 

use of, reasons for 205 

Temperatures, high, pro(iucecl during air compression, clangers of 101 

Tenders, contract 458-460 

Terry, Tench and Proctor, tunneling machine of, features of 185 

Tequiquac tunnel (Mexico), details of 21 

Terre-noir tunnel (France), mention of 14 

Thawing of explosives, proper method of 258 

Thaw houss, construction of 258 

heating of 259 

Thermal efficiency, influence of, on choice of power 75 

Tiefe Georg StoUen (Germany), details of 15 

Timber, for roof support, advantages of 270 

preparation of 270 

preservative treatment of 270-273 

seasoned, advantages of 270 

selection of 292 

square versus round, choice of 271 

Timbering, adequate importance of 292 

American system 510-51 1 

arrangement of, in tunnel 273-278 

defined 42 1 

delay in, danger of 292 

foreign systems 461, 510 

for wet tunnels, figure showing 275, 276 

in soft ground; importance of careful work 516-517 

materials for 270 

necessity of bracing 423 

needle beams 517 

of heading, method of 283 

of swelling ground, method o*" 279 

swinging false set system of 282 

tail-block system of 281 

Timber lining 433 

Tipple 475 

Torches, danger in use of 314 

Totley tunnel (England), details of 30 

Track, haulage, gage 471-472 

maintenance 473 

Tramming, dangers in 309, 310 

Transmission of power, means of 64 

Transvaal, ventilation requirements in 115 

Trench type, cost of 566-567 

Trolley wires, danger from 311 

Tsude Adit (Japan), mention of 33 

Tunnel, definition of 2 



610 INDEX 



PAGE 



Tunnel cars, data concerning, table giying 169 

figure showing. . 164-168 

types of 164-170 

data, outline of (appendix) 577-582 

Tunnel headings, direction of holes in 221 

number of holes in, table showing 219 

Tunneling machines, features of . . 181 

patents for, list of 188-201 

requirements of 184 

types of 185-187 

use of, in English Channel tunnel 183 

Turbine-wheels, as sources of power 55 

efficiency of 57 

features of , 55 

steam, efficiency of 58 

features of ^ 58 

Turbo-compressors, advantages of 109 

effectiveness of 92 

features of 91-93 

figure showing 95 

power required by 82 

section through, figure showing 93 

use of, for ventilation 112 

U 

United States Reclamation Service, officials of, acknowledgments to 3 

United States, early railway tunnels in 14 

Unloaders for air compressors, use of 99 

Utah Metals tunnel (Utah), air pressure used at 103 

blast holes in, depth of 235 

order of 220 

car used at, features of 159 

direction of air current in 114 

drilling speed at 151 

features of 48 

grade of dynamite used in 241 

power plant of, water supply for 66 

pressure of ventilating current 120 

system of lighting 202 

V 

V-cut, arrangement of holes in 226 

Valveless air drills, merits of 156 

Valve, butterfly, figure showing ; 134 

merits of 156 

tappet, advantages of 155 



INDEX 611 

PAGE 

Ventilating current, air needed for 1 15, 1 16 

arrangement of pipes for, figure showing 113 

direction of, factors influencing 113 

machinery for in 

pressure of 118, 119 

size of pipe line for 121, 122 

Ventilating machinery, selection of, factors determining 123 

Ventilating pipe, capacity of, table showing 120 

Ventilation 456, 476-477 

of ancient tunnels 10 

of tunnels, air required for 115, 116 

Vertical column mounting for drills, merits of 214 

Volumetric efficiency of air compressors 83 

VV 

Wallkill Siphon tunnel (N. Y.), air pressure used at 103 

blast holes in, depth of 235 

order of 220 

car used at, features of 169 

direction of air current in 114 

drilling speed at 151 

grade of dynamite used in 241 

quantity of explosives used in 243 

Waterproofing cast-iron lining 442-444, 448-451 

Water, rushes of, danger from 315 

for fire protection, need of 314 

Water power, selection of, conditions determining 78 

Water wheels, cost of installation of 66 

efficiency of 57 

impulse type, regulation of 98 

turbine type, details of 55 

use of 55 

Wedge cut, description of 221 

figure showing 223 

Welfare work in camps 481 

Widest tunnel in the world 421 

Wood lining 553 

Woolwich tunnel (England), power plant of, fuel consumption of 75 

use of gas-producers at 50 

Y 

Yak tunnel (Colo,), air pressure at 103 

blast holes in, depth of 235 

order of 220 

car used at, features of 169 

cost of drill repairs at 153 



612 INDEX 

PAGIE 

Yale tunnel (Colo.), direction of air current in 114 

features of 48 

grade of dynamite used in 241 

pyramid cut in, figure showing 224 

Yonkers Siphon tunnel (N. Y.), features of 38 

Z 

Zinc chloride as timber preservative 271 



%. 









^A^ 



-c^^^, » 






'^.^ v*^ 



'^^ >*■ 



^.-v 



